[cogl] build: add newly introduced header to fix make dist

[Rico Tzschichholz <ricotz src gnome org>]

commit 1674cf28f1f5b71bd25a1f253c99825d427dd243
Author: Rico Tzschichholz <ricotz t-online de>
Date:   Tue May 22 15:17:11 2012 +0200

    build: add newly introduced header to fix make dist
    
    Missing bit of 4bb6eff3dbd50d8fef7d6bdbed55c5aaa70036a8
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 cogl/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/cogl/Makefile.am b/cogl/Makefile.am
index 3c5500c..ef703a5 100644
--- a/cogl/Makefile.am
+++ b/cogl/Makefile.am
@@ -343,6 +343,7 @@ cogl_sources_c = \
 	$(srcdir)/cogl-memory-stack.c			\
 	$(srcdir)/cogl-magazine-private.h		\
 	$(srcdir)/cogl-magazine.c			\
+	$(srcdir)/cogl-gles2-context-private.h		\
 	$(srcdir)/cogl-gles2-context.c			\
 	$(NULL)