[build] Link against -lm

Fedora 13 uses --no-add-needed, so if we use -lm, we have
to explicitly specify it.

More information: http://fedoraproject.org/wiki/Features/ChangeInImplicitDSOLinking

src/Makefile-big.am

@@ -51,7 +51,7 @@ big-enum-types.c: stamp-big-enum-types.h big/big-enum-types.c.in
 
 noinst_LTLIBRARIES += libbig-1.0.la
 
-libbig_1_0_la_LIBADD = $(BIG_LIBS)
+libbig_1_0_la_LIBADD = -lm $(BIG_LIBS)
 libbig_1_0_la_SOURCES = \
 	$(big_source_c) \
 	$(big_source_h) \

src/Makefile-st.am

@@ -144,7 +144,7 @@ st_source_c =					\
 
 noinst_LTLIBRARIES += libst-1.0.la
 
-libst_1_0_la_LIBADD = $(ST_LIBS)
+libst_1_0_la_LIBADD = -lm $(ST_LIBS)
 libst_1_0_la_SOURCES =				\
     $(st_source_c)				\
     $(st_source_private_h)			\

src/Makefile.am

@@ -151,7 +151,7 @@ shell-marshal.c: Makefile shell-marshal.list
 	rm -f xgen-smc
 
 libgnome_shell_la_LDFLAGS = -avoid-version -module
-libgnome_shell_la_LIBADD =	\
+libgnome_shell_la_LIBADD =-lm \
 	$(MUTTER_PLUGIN_LIBS)	\
         $(LIBGNOMEUI_LIBS)      \
 	libbig-1.0.la		\