Prepare upcoming GCC 4.8 release.

o Add -Wno-unused-parameter -Wno-unused-but-set-parameter to suppress
  new warnings.
o Define GCC_COLORS to enable colorful diagnostic messages.

Change-Id: Icbd62300b0e6f39d4e514edec2431a06b4d72421
(cherry picked from internal commit ccd8e6082b5b1e519a75068fa6c887a1a85b53c4)
diff --git a/envsetup.sh b/envsetup.sh
index d64bd29..3639db9 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -205,6 +205,8 @@
     set_sequence_number
 
     export ANDROID_BUILD_TOP=$(gettop)
+    # With this environment variable new GCC can apply colors to warnings/errors
+    export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'
 }
 
 function set_sequence_number()