c1x --> c11

[Mike Stump]

One last straggler I found:

Tested on x86_64-apple-darwin12.

Committed revision 203928.

Index: builtin-complex-err-1.c
===================================================================
--- builtin-complex-err-1.c     (revision 203926)
+++ builtin-complex-err-1.c     (working copy)
@@ -1,6 +1,6 @@
 /* Test __builtin_complex errors.  */
 /* { dg-do compile } */
-/* { dg-options "-std=c1x -pedantic-errors" } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
 
 typedef double D;