Moving y4m encoding functions into separate files.

Change-Id: I03f614872167841515a74740d654c008b60104a4
diff --git a/examples.mk b/examples.mk
index 66b719c..6befa50 100644
--- a/examples.mk
+++ b/examples.mk
@@ -26,6 +26,7 @@
 vpxdec.SRCS                 += ivfdec.c ivfdec.h
 vpxdec.SRCS                 += tools_common.c tools_common.h
 vpxdec.SRCS                 += webmdec.c webmdec.h
+vpxdec.SRCS                 += y4menc.c y4menc.h
 vpxdec.SRCS                 += nestegg/halloc/halloc.h
 vpxdec.SRCS                 += nestegg/halloc/src/align.h
 vpxdec.SRCS                 += nestegg/halloc/src/halloc.c