Move image matching functions to common location.

Exact same functions were present in two encoder binaries.

BUG=aomedia:442

Change-Id: Ib169c29cee8ae40cbd71c26099a3339ec7143315
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 98b81eb..21a29b6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,7 +125,9 @@
     "${AOM_ROOT}/warnings.c"
     "${AOM_ROOT}/warnings.h"
     "${AOM_ROOT}/y4minput.c"
-    "${AOM_ROOT}/y4minput.h")
+    "${AOM_ROOT}/y4minput.h"
+    "${AOM_ROOT}/examples/encoder_util.h"
+    "${AOM_ROOT}/examples/encoder_util.c")
 
 set(AOM_ENCODER_STATS_SOURCES
     "${AOM_ROOT}/aomstats.c"