Provide option to swap bytes for 16 bit colormodes

Color modes: RGB_565 & RGBA_4444
Change-Id: I571b6832b9848e5c4109272978f68623ca373383
diff --git a/makefile.unix b/makefile.unix
index b027786..23e811f 100644
--- a/makefile.unix
+++ b/makefile.unix
@@ -53,6 +53,9 @@
 # Extra flags to enable experimental features and code
 # EXTRA_FLAGS += -DWEBP_EXPERIMENTAL_FEATURES
 
+# Extra flags to enable byte swap for 16 bit colorspaces.
+# EXTRA_FLAGS += -DWEBP_SWAP_16BIT_CSP
+
 # Extra flags to enable multi-threading
 EXTRA_FLAGS += -DWEBP_USE_THREAD
 EXTRA_LIBS += -lpthread