[gtk+] gtkswitch.c: Fix Build on C89 Compilers

[Chun-wei Fan <fanchunwei src gnome org>]

commit e31a936e3e9b26cee35f51b6bd822803539c59db
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Mar 3 12:14:24 2015 +0800

    gtkswitch.c: Fix Build on C89 Compilers
    
    This file now uses round(), which was not available until C99, so include
    fallback-c89.c instead of math.h, which includes math.h and does a fallback
    implementation of round().

 gtk/gtkswitch.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkswitch.c b/gtk/gtkswitch.c
index 1f5692c..1ab12b5 100644
--- a/gtk/gtkswitch.c
+++ b/gtk/gtkswitch.c
@@ -53,7 +53,7 @@
 #include "gtkactionhelper.h"
 #include "gtkwidgetprivate.h"
 
-#include <math.h>
+#include "fallback-c89.c"
 
 #define DEFAULT_SLIDER_WIDTH    (36)