Make Perl headers less noisy under -pedantic.
Make UNUSED_VAR macro available in CFC.
Fix unused vars.

Address some compiler warnings by either removing or tagging unused
variables.
Use macro instead of const int to avoid warning.

Avoid -pedantic warnings under Clang regarding variable-length arrays by
using a macro rather than const integer type.
Use `static const` rather than `const static`.
Change some int signs to avoid compiler warnings.