Avoid printf ("%s", NULL) in posix/bug-regex22.c.

Building posix/bug-regex22.c fails with GCC mainline because of
-Wformat-overflow= warnings for NULL arguments to %s formats.

This is *not* testing how glibc handles such format arguments; in the
context of the messages in question it makes no sense to pass NULL to
such a %s format (the code passes s, inside "if (s == NULL)").  So
this patch changes the code not to pass such a format argument at all
(which means the string passed is constant, so no need to use printf
at all - however, there are two separate tests here with different
length arguments passed to re_compile_pattern, so it *does* make sense
to make the strings used different so that in the event of failure
it's clear which one of the tests failed).

Tested with build-many-glibcs.py with GCC mainline for
aarch64-linux-gnu.

	* posix/bug-regex22.c (main): Use puts with distinct error
	messages for unexpected success of re_compile_pattern, not printf
	with NULL argument to %s.

ChangeLog

@@ -1,5 +1,9 @@
 2018-11-01  Joseph Myers  <joseph@codesourcery.com>
 
+	* posix/bug-regex22.c (main): Use puts with distinct error
+	messages for unexpected success of re_compile_pattern, not printf
+	with NULL argument to %s.
+
 	* stdio-common/bug22.c: Include <libc-diag.h>.
 	(do_test): Disable -Wformat-overflow= warnings around fprintf
 	calls outputting more than INT_MAX characters.

posix/bug-regex22.c

@@ -99,8 +99,8 @@ main (void)
   s = re_compile_pattern ("[[:DIGIT:]]", 11, &re);
   if (s == NULL)
     {
-      printf ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: %s\n",
-	      s);
+      puts ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: "
+	    "length 11");
       result = 1;
     }
 
@@ -109,8 +109,8 @@ main (void)
   s = re_compile_pattern ("[[:DIGIT:]]", 2, &re);
   if (s == NULL)
     {
-      printf ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: %s\n",
-	      s);
+      puts ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: "
+	    "length 2");
       result = 1;
     }