Avoid undefined behavior when strcoll fails,

Avoid undefined behavior when strcoll fails,
by resorting the directory with strcmp instead.

Include <setjmp.h>.
Include "quote.h".
(compare_atime, rev_cmp_atime, compare_ctime, rev_cmp_ctime,
compare_mtime, rev_cmp_mtime, compare_size, rev_comp_size,
compare_name, rev_cmp_name, compare_extension, rev_cmp_extension,
compare_version, rev_compare_version): Move before use, so that
we can remove the forward declaration.  Reimplement in terms of
the new functions described below, using xstrcoll instead of strcoll.
(failed_strcoll): New var.
(xstrcoll): New function.
(V): New type.
(cmp_ctime, compstr_ctime, rev_str_ctime): New functions.
(cmp_mtime, compstr_mtime, rev_str_mtime): Likewise.
(cmp_atime, compstr_atime, rev_str_atime): Likewise.
(cmp_size, compstr_size, rev_str_size): Likewise.
(cmp_version): Likewise.
(cmp_name, compstr_name, rev_str_name): Likewise.
(cmp_extension, compstr_extension, rev_str_extension): Likewise.
(sort_files): Use prototype for internal function var.
If the strcoll-based comparison fails, fall back on a strcmp-based one.