Update libtheora to 1.2.0 release.

Makefile

@@ -24,7 +24,7 @@ HARFBUZZ_BRANCH := 10.1.0
 # Project versions (for downloadable tars)
 LIBOGG_VERSION := 1.3.5
 LIBVORBIS_VERSION := 1.3.7
-LIBTHEORA_VERSION := 1.2.0alpha1
+LIBTHEORA_VERSION := 1.2.0
 FT_VERSION := 2.13.3
 BZIP2_VERSION := 1.0.8
 LIBMODPLUG_VERSION := 0.8.8.5