[gtksourceview] build: include math.h

[Christian Hergert <chergert src gnome org>]

commit 66e7f1983775dfaf60eaad8f984e03ace4d2989c
Author: Christian Hergert <chergert redhat com>
Date:   Mon Jun 21 20:32:02 2021 -0700

    build: include math.h

 gtksourceview/gtksourcemap.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtksourceview/gtksourcemap.c b/gtksourceview/gtksourcemap.c
index 038f90e7..39b45dbe 100644
--- a/gtksourceview/gtksourcemap.c
+++ b/gtksourceview/gtksourcemap.c
@@ -18,6 +18,7 @@
 
 #include "config.h"
 
+#include <math.h>
 #include <string.h>
 
 #if ENABLE_FONT_CONFIG