[gtkmm] Fix the build.

[Murray Cumming <murrayc src gnome org>]

commit dfd6e033d55411cb05310c69f7e55514c21b8612
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Feb 22 14:49:22 2012 +0100

    Fix the build.

 gtk/src/texttag.hg |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gtk/src/texttag.hg b/gtk/src/texttag.hg
index dbd9c4d..13cab3c 100644
--- a/gtk/src/texttag.hg
+++ b/gtk/src/texttag.hg
@@ -23,6 +23,7 @@
 #include <glibmm/object.h>
 #include <gtkmm/enums.h>
 #include <gdkmm/color.h>
+#include <gdkmm/rgba.h>
 #include <pangomm/fontdescription.h>
 #include <pangomm/tabarray.h>