next no longer compiles on non-gnu platforms

FYI

Since 83c0e5ad 'Add string comparison functions that respect the
ignore_case variable.' was merged to next, it can't be compiled on
platforms without the GNU FNM_CASEFOLD extension to fnmatch.

If we're going this route, then non-gnu platforms will need to
build with the fnmatch in compat/ and Makefile will need a
NO_FNMATCH define.

-Brandon