Don't play with fnmatch.c replacement

[lumag]

Currently fnmatch.c, even if it is selected, conditionally disables compilation of fnmatch() funciton even though the rest of the code expects to get it (e.g. because Autoconf didn't detect the working implementation and enabled fnmatch.c to replace it). Drop the extra conditionals, to fix Autoconf magic.

Observed error:

ld: src/cabextract.o: in function process_cabinet': /usr/src/debug/cabextract/1.11/src/cabextract.c:499:(.text.startup+0xf1c): undefined reference to rpl_fnmatch' collect2: error: ld returned 1 exit status