Further improve FreeBSD support

[danfe]

Two weeks ago I've added FSearch to FreeBSD Ports Collection. It required couple of changes in order to build that addressed certain Linux'isms. One of them (unconditional inclusion of linux/limits.h) was fixed in 917442e. The other issue seemingly remains: use of non-standard strverscmp() function.

This function is a GNU extension and thus is not present in other libc implementations, including (but not limited to) FreeBSD's. It turns out that it can be implemented using g_utf8_collate_key_for_filename() calls on compared strings (see the patches under files directory at the svnweb link above). This is probably better than writing strverscmp() implementation from scratch since FSearch is GTK/Glib application anyway, so it's OK to depend on functions offered by those APIs.

I did not wrap the code with any #ifndef __GNUC__ guards since there is no conflict to prevent in case of FreeBSD, and arguably it is better not to rely on some non-standard function in the first place (i.e., I'd probably simply used provided reference implementation under some non-clashy-with-GNUs-strverscmp name, regardless of the operating system and/or underlying standard C library).

[cboxdoerfer]

Awesome thank you. I'll have a look at your patches.