[cogl] build: Use -Wundef when possible

[Damien Lespiau <dlespiau src gnome org>]

commit 53ddc20fe9cd1400d18274e521932f84a4aecc5b
Author: Damien Lespiau <damien lespiau intel com>
Date:   Sat Dec 29 03:07:52 2012 +0000

    build: Use -Wundef when possible
    
    This allows us to catch the use of undefined macros (that default to 0)
    in preprocessor conditionals.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 32e95f7..e247bcb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -300,7 +300,7 @@ AC_ARG_ENABLE(
 
 MAINTAINER_COMPILER_FLAGS="-Wall -Wcast-align -Wuninitialized
                            -Wno-strict-aliasing -Wempty-body -Wformat
-                           -Wformat-security -Winit-self
+                           -Wformat-security -Winit-self -Wundef
                            -Wdeclaration-after-statement -Wvla
                            -Wpointer-arith -Wmissing-declarations"