Include <string.h> instead of <stdlib.h>.
Do not include <assert.h>; no longer needed.
Include xalloc.h.
(memrchr): Remove decl.
(dir_name_r): Remove.
(dir_len): Renamed from dirlen. All callers changed.
Rewrite in terms of base_name, for simplicity and consistency.
(dir_name): Never return NULL. All callers changed.
Do not include <stdlib.h> in test program; no longer needed.
return 0; is fine for test program.
(dir_name_r): Declare this function as static.
[BACKSLASH_IS_PATH_SEPARATOR]: Fix a bug that'd
manifest itself on a name containing a mix of slashes and
backslashes.
Make this function work with names starting with a DOS-style
drive letter and colon prefix.
(dir_name): Append `.' if necessary.
Based mostly on patches from Prashant TR and Eli Zaretskii.
(dir_name): Remove the restriction that there be no
trailing slashes. Now, this code skips past them, effectively
ignoring them.
[TEST_DIRNAME] (main): New unit tests.
(BACKSLASH_IS_PATH_SEPARATOR): Define.
(dir_name) [BACKSLASH_IS_PATH_SEPARATOR]: Handle the case in which
both `\' and `/' may be use as path separators.
Based on a patch from Prashant TR.
