stdio-common: Include <libc-internal.h> in some tests

This patch adds the missing libc-internal.h include on test-vprintf.c
tst-sprintf.c.

ChangeLog

@@ -1,3 +1,8 @@
+2014-12-15  Adhemerval Zanella  <Azanella@linux.vnet.ibm.com>
+
+	* stdio-common/test-vfprintf.c: Include <libc-internal.h>.
+	* stdio-common/tst-sprintf.c: Likewise.
+
 2014-12-15  Torvald Riegel  <triegel@redhat.com>
 
 	* sysdeps/unix/sysv/linux/s390/pthread_once.c: Remove file.

stdio-common/test-vfprintf.c

@@ -25,6 +25,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>
+#include <libc-internal.h>
 
 
 const char *locs[] =

stdio-common/tst-sprintf.c

@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <locale.h>
 #include <string.h>
+#include <libc-internal.h>
 
 
 static int