Fix y4m monochrome output; split raw/y4m logic

BUG=aomedia:2091

Change-Id: I2eed6a0b70c57415b323b7e8207592a7fdebba2b
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c99dbed..8f209ae 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -132,6 +132,8 @@
             "${AOM_ROOT}/common/tools_common.c"
             "${AOM_ROOT}/common/tools_common.h"
             "${AOM_ROOT}/common/video_common.h"
+            "${AOM_ROOT}/common/rawenc.c"
+            "${AOM_ROOT}/common/rawenc.h"
             "${AOM_ROOT}/common/y4menc.c"
             "${AOM_ROOT}/common/y4menc.h")