minor performance improvement to getcwd.c

[Paul Eggert]

I installed this:

2007-03-19  Paul Eggert  <address@hidden>

        * lib/getcwd.c (__getcwd): Remove redundant comparison of buf to NULL.
        If size is zero here, buf must be zero.

--- lib/getcwd.c        21 Feb 2007 20:50:00 -0000      1.23
+++ lib/getcwd.c        19 Mar 2007 17:30:04 -0000
@@ -391,7 +391,7 @@ __getcwd (char *buf, size_t size)
   used = dir + allocated - dirp;
   memmove (dir, dirp, used);

-  if (buf == NULL && size == 0)
+  if (size == 0)
     /* Ensure that the buffer is only as large as necessary.  */
     buf = realloc (dir, used);