[lasem] mathml: fix build on OSX

[Emmanuel Pacaud <emmanuel src gnome org>]

commit 8b018ccda0e38aad5ebb3a217d1cc4dbf20691b5
Author: Emmanuel Pacaud <emmanuel gnome org>
Date:   Thu Feb 2 08:54:44 2012 +0100

    mathml: fix build on OSX
    
    Fix https://bugzilla.gnome.org/show_bug.cgi?id=669225.
    
    When building lasem on Mac OS X 10.6 ( gcc 4.2 ), the build failed in linking
    as:
    
    ld: duplicate symbol _lsm_mathml_bbox_null in .libs/lsmmathmlenumtypes.o and
    .libs/lsmdomparser.o

 src/lsmmathmlutils.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/lsmmathmlutils.h b/src/lsmmathmlutils.h
index 20124e5..c71d58b 100644
--- a/src/lsmmathmlutils.h
+++ b/src/lsmmathmlutils.h
@@ -35,7 +35,7 @@ typedef struct {
 	gboolean is_defined;
 } LsmMathmlBbox;
 
-const LsmMathmlBbox lsm_mathml_bbox_null;
+extern const LsmMathmlBbox lsm_mathml_bbox_null;
 
 void 	lsm_mathml_bbox_add_horizontally 		(LsmMathmlBbox *bbox, const LsmMathmlBbox *new_bbox);
 void 	lsm_mathml_bbox_add_over 			(LsmMathmlBbox *self, const LsmMathmlBbox *bbox);