Add ftmm.c to FreeType build.

The FreeType configuration is already building with
TT_CONFIG_OPTION_GX_VAR_SUPPORT, but the functions cannot be accessed
without base/ftmm.c. The ftmm.c file is small and simply exposes the
means to call the service which already exists on the ft_face.

Change-Id: I35cab20abd0194df1c5be7b0ebb09cc8c260a470
diff --git a/Android.mk b/Android.mk
index 2010736..ae098d1 100644
--- a/Android.mk
+++ b/Android.mk
@@ -26,6 +26,7 @@
 	src/base/ftsystem.c \
 	src/base/ftinit.c \
 	src/base/ftgasp.c \
+	src/base/ftmm.c \
 	src/gzip/ftgzip.c \
 	src/raster/raster.c \
 	src/sfnt/sfnt.c \