Prefer readlink to lstat+S_ISLNK when easy

To test for a symlink, use readlink, not lstat+S_ISLNK,
when the lstat is used only for the symlink test.
This avoids EOVERFLOW issues.
* lib/lchown.c (rpl_lchown) [CHOWN_CHANGE_TIME_BUG]:
* lib/rename.c (rpl_rename):
[!(_WIN32 && !__CYGWIN__) && (RENAME_TRAILING_SLASH_SOURCE_BUG
|| RENAME_DEST_EXISTS_BUG || RENAME_HARD_LINK_BUG)]:
* lib/renameatu.c (renameatu):
[HAVE_RENAMEAT && RENAME_TRAILING_SLASH_SOURCE_BUG]:
* lib/unlink.c (rpl_unlink):
* lib/unlinkat.c (rpl_unlinkat):
* lib/utimens.c (lutimens) [!HAVE_LUTIMENS]:
Prefer readlink to lstat+S_ISLNK.
* modules/lchown, modules/rename, modules/unlink, modules/utimens:
(Depends-on): Add readlink.
* modules/unlinkat (Depends-on): Add fstatat, readlinkat.

modules/lchown

@@ -7,7 +7,7 @@ m4/lchown.m4
 
 Depends-on:
 unistd-h
-readlink        [test $HAVE_LCHOWN = 0]
+readlink        [test $HAVE_LCHOWN = 0 || test $REPLACE_LCHOWN = 1]
 chown           [test $HAVE_LCHOWN = 0 || test $REPLACE_LCHOWN = 1]
 errno-h         [test $HAVE_LCHOWN = 0 || test $REPLACE_LCHOWN = 1]
 bool            [test $HAVE_LCHOWN = 0 || test $REPLACE_LCHOWN = 1]

modules/rename

@@ -12,6 +12,7 @@ chdir             [test $REPLACE_RENAME = 1]
 dirname-lgpl      [test $REPLACE_RENAME = 1]
 free-posix        [test $REPLACE_RENAME = 1]
 lstat             [test $REPLACE_RENAME = 1]
+readlink          [test $REPLACE_RENAME = 1]
 rmdir             [test $REPLACE_RENAME = 1]
 same-inode        [test $REPLACE_RENAME = 1]
 stat              [test $REPLACE_RENAME = 1]

modules/unlink

@@ -10,6 +10,7 @@ unistd-h
 filename        [test $REPLACE_UNLINK = 1]
 lstat           [test $REPLACE_UNLINK = 1]
 malloc-posix    [test $REPLACE_UNLINK = 1]
+readlink        [test $REPLACE_UNLINK = 1]
 
 configure.ac:
 gl_FUNC_UNLINK

modules/unlinkat

@@ -21,6 +21,8 @@ openat-die      [test $HAVE_UNLINKAT = 0]
 rmdir           [test $HAVE_UNLINKAT = 0]
 save-cwd        [test $HAVE_UNLINKAT = 0]
 unlink          [test $HAVE_UNLINKAT = 0]
+fstatat         [test $REPLACE_UNLINKAT = 1]
+readlinkat      [test $REPLACE_UNLINKAT = 1]
 
 configure.ac:
 gl_FUNC_UNLINKAT

modules/utimens

@@ -15,6 +15,7 @@ fstat
 lstat
 gettime
 msvc-nothrow
+readlink
 stat
 stat-time
 bool