<AWT Dev> RFR: 8080317: Disable warning treated as error for signed/unsigned comparison in building splashscreen

[Phil Race]

Warnings are now treated as errors by default.
I need a quick review on this from anyone who is available so I can fix 
our build for integration...

-phil.

https://bugs.openjdk.java.net/browse/JDK-8080317

$ hg diff make/lib/Awt2dLibraries.gmk
diff --git a/make/lib/Awt2dLibraries.gmk b/make/lib/Awt2dLibraries.gmk
--- a/make/lib/Awt2dLibraries.gmk
+++ b/make/lib/Awt2dLibraries.gmk
@@ -885,10 +885,10 @@
        OPTIMIZATION := LOW, \
        CFLAGS := $(LIBSPLASHSCREEN_CFLAGS) $(CFLAGS_JDKLIB) \
                  $(GIFLIB_CFLAGS) $(LIBJPEG_CFLAGS) $(PNG_CFLAGS), \
-      DISABLED_WARNINGS_gcc := type-limits unused-result 
maybe-uninitialized, \
+      DISABLED_WARNINGS_gcc := sign-compare type-limits unused-result 
maybe-uninitialized, \
        DISABLED_WARNINGS_clang := incompatible-pointer-types, \
        DISABLED_WARNINGS_solstudio := E_NEWLINE_NOT_LAST 
E_DECLARATION_IN_CODE, \
-      DISABLED_WARNINGS_microsoft := 4244 4267, \
+      DISABLED_WARNINGS_microsoft := 4018 4244 4267, \
        MAPFILE := 
$(JDK_TOPDIR)/make/mapfiles/libsplashscreen/mapfile-vers, \
        LDFLAGS := $(LDFLAGS_JDKLIB) \
            $(call SET_SHARED_LIBRARY_ORIGIN), \