Removed multiple old-style (C) casts and replaced them with the
appropriate _cast's. This makes httplib a better citizen inside projects
that are compiled with all warnings enabled.
Unfortunately one warning remains as a result of invoking an
OpenSSL macro (at least on Linux), that would have to be fixed
upstream.
Also fixed a few casts for invocations of setsockopt.
setsockopt takes a const void* for the value pointer, not a char*.
Well, except on Windows ...
Co-authored-by: Andre Eisenbach <git@4ae.us>
