This is a fork of libdisasm that hacks^H^H^H^H^H adds in very basic 64 bit support. There's still a lot of work to do to fully support SSE and other instructions that are standard in 64 bit instruction sets.
I have primarily been hacking this to support Line. It currently only builds under Mac OS but I will fix that soon.
The API for libdisasm is in libdisasm/libdis.h, which is installed in $prefix/include after "make install".