Fails to compile with newer library versions (libssl?)

[spang]

I'm trying to compile brubeck on Debian Sid with the following library versions:

➜ brubeck git:(master) ✗ dpkg -l libmicrohttpd-dev libjansson-dev libssl-dev gcc
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-=======================================-========================-========================-====================================================================================
ii gcc 4:6.1.1-1 amd64 GNU C compiler
ii libjansson-dev:amd64 2.7-5 amd64 C library for encoding, decoding and manipulating JSON data (dev)
ii libmicrohttpd-dev 0.9.51-1 amd64 library embedding HTTP server functionality (development)
ii libssl-dev:amd64 1.1.0b-2 amd64 Secure Sockets Layer toolkit - development files

It fails to compile with this error:

➜ brubeck git:(master) ✗ ./script/bootstrap
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/backend.c -o src/backend.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/backends/carbon.c -o src/backends/carbon.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/bloom.c -o src/bloom.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/city.c -o src/city.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/histogram.c -o src/histogram.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/ht.c -o src/ht.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/http.c -o src/http.o
src/http.c: In function ‘expire_metric’:
src/http.c:67:3: warning: ‘MHD_create_response_from_data’ is deprecated: MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer() [-Wdeprecated-declarations]
 return MHD_create_response_from_data(
 ^~~~~~
In file included from src/http.c:4:0:
/usr/include/microhttpd.h:2079:1: note: declared here
 MHD_create_response_from_data (size_t size,
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/http.c: In function ‘send_metric’:
src/http.c:100:3: warning: ‘MHD_create_response_from_data’ is deprecated: MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer() [-Wdeprecated-declarations]
 return MHD_create_response_from_data(
 ^~~~~~
In file included from src/http.c:4:0:
/usr/include/microhttpd.h:2079:1: note: declared here
 MHD_create_response_from_data (size_t size,
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/http.c: In function ‘send_stats’:
src/http.c:177:2: warning: ‘MHD_create_response_from_data’ is deprecated: MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer() [-Wdeprecated-declarations]
 return MHD_create_response_from_data(
 ^~~~~~
In file included from src/http.c:4:0:
/usr/include/microhttpd.h:2079:1: note: declared here
 MHD_create_response_from_data (size_t size,
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/http.c: In function ‘send_ping’:
src/http.c:210:2: warning: ‘MHD_create_response_from_data’ is deprecated: MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer() [-Wdeprecated-declarations]
 return MHD_create_response_from_data(
 ^~~~~~
In file included from src/http.c:4:0:
/usr/include/microhttpd.h:2079:1: note: declared here
 MHD_create_response_from_data (size_t size,
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/http.c: In function ‘handle_request’:
src/http.c:244:3: warning: ‘MHD_create_response_from_data’ is deprecated: MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer() [-Wdeprecated-declarations]
 response = MHD_create_response_from_data(
 ^~~~~~~~
In file included from src/http.c:4:0:
/usr/include/microhttpd.h:2079:1: note: declared here
 MHD_create_response_from_data (size_t size,
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/internal_sampler.c -o src/internal_sampler.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/log.c -o src/log.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/metric.c -o src/metric.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/sampler.c -o src/sampler.o
gcc -g -Wall -O3 -Wno-strict-aliasing -Isrc -Ivendor/ck/include -DNDEBUG=1 -DGIT_SHA=\"dad4b3b\" -DBRUBECK_HAVE_MICROHTTPD -c src/samplers/statsd-secure.c -o src/samplers/statsd-secure.o
src/samplers/statsd-secure.c: In function ‘statsd_secure__thread’:
src/samplers/statsd-secure.c:101:11: error: storage size of ‘ctx’ isn’t known
 HMAC_CTX ctx;
 ^~~
src/samplers/statsd-secure.c:111:2: warning: implicit declaration of function ‘HMAC_CTX_init’ [-Wimplicit-function-declaration]
 HMAC_CTX_init(&ctx);
 ^~~~~~~~~~~~~
src/samplers/statsd-secure.c:152:2: warning: implicit declaration of function ‘HMAC_CTX_cleanup’ [-Wimplicit-function-declaration]
 HMAC_CTX_cleanup(&ctx);
 ^~~~~~~~~~~~~~~~
src/samplers/statsd-secure.c:101:11: warning: unused variable ‘ctx’ [-Wunused-variable]
 HMAC_CTX ctx;
 ^~~
Makefile:44: recipe for target 'src/samplers/statsd-secure.o' failed
make: *** [src/samplers/statsd-secure.o] Error 1

I suspect OpenSSL 1.1, but haven't yet looked into it extensively. The program compiles just fine on a machine running Debian 8 with OpenSSL 1.0.1t.