tests: set C11, enable pedantic warnings, fix GCC and Clang warnings
Changes:
- Set the standard of the test suite from
gnu11
toc11
. Would be nice to prevent all the GNUisms creeping in the test suite while it's easy to do so. - Enabled pedantic warnings.
- Fixed all warnings generated by GCC and Clang, except the unused function warnings in
netdb.c
. That test looks work-in-progress, didn't wanted to touch it. - Disabled one test case that used a GNU specific extension (zero-sized arrays).