C Client compilation issues in 3.5.7-rc

The C client included in release-3.5.7-rc0 and release-3.5.7-rc1 suffers from a few issues:

1. It configures, but "forgets" to build the C code in the full-build profile;
2. Compilation actually fails with GCC 8.3, as the the Makefile uses -Werror and the compiler detects a couple possible buffer overruns;
3. The WIN32 branch of the code does not compile because of a change in socket representation.

This should probably be set to "blocker," but I don't know if the C client is supposed to block a release. Oh, and the first issue, at least, also existed in 3.5.6—and it seems nobody complained 

A "pull request" is in the works.