Remove deprecated iconv INI settings

[Girgias]

Analogous to #5334 for iconv

[Girgias]

@nikic@cmb69 can one of you have a look at this again and tell me if I can merge this into master?

[cmb69]

Thanks for working on this! I'm not really sure what to do with iconv_set_encoding() and iconv_get_encoding(); since they don't have been already deprecated, it might be best to deprecate them now, but to keep the functionality. Or maybe not, since it'd be somehow confusing.

[Girgias]

Thanks for working on this! I'm not really sure what to do with iconv_set_encoding() and iconv_get_encoding(); since they don't have been already deprecated, it might be best to deprecate them now, but to keep the functionality. Or maybe not, since it'd be somehow confusing.

I've deprecated both of them not sure how to go about preserving functionality tho as it would seem weirdly convoluted.

[Girgias]

If there are no objections I'll merge this at the end of the week.

[nikic]

For both this one and #5334:

• What is the state regarding different encoding names in iconv and mbstring? Did you check that they support the same set of encodings?
• This PR deprecates iconv_set_encoding() and converts it into a no-op, while the mbstring PR retrains the mb_internal_encoding() etc functionality. At the least this is inconsistent, but I don't know what the right solution is.

[krakjoe]

Closing because out of date, conflicting, and I'm not sure if it's still applicable, or if open questions were ever resolved (away from here).

If I'm wrong, open a fresh PR against master and move quickly ;)