File::Glob: silence some compiler warnings

File::Glob: silence some compiler warnings

In bsd_glob.c, there are nested set of functions glob0(), glob1() etc,
which among their parameters pass a pointer to a compiled pattern, and also
to its end. It turns out the end pointer isn't usually used, since the
pattern is usually scanned for BG_EOS instead. Also, glob3() is
passed two pattern ranges, both within the same pattern, and both with
the same pointer to the end of the pattern buffer. Since both end pointers
are the same, eliminate one of them. This removed an unused var compiler
warning. Use the remaining end pointer in the glob*() functions to add
assertions that we haven't fallen off the end of the buffer.

Finally, ARG_MAX may be signed.