JDK 9 RFR of JDK-8032734: Add cast lint warning to build of jdk repository

[Joe Darcy]

Hello,

Work has started to clear the jdk repo of the "cast" category of lint 
warnings (JDK-8032733, "Fix cast lint warnings in client libraries"). 
Anticipating the time when those warnings are cleared, I'd like to now 
get a code review of JDK-8032734 "Add cast lint warning to build of jdk 
repository" which will enable that warning in the build:

diff -r 78d907730378 make/Setup.gmk
--- a/make/Setup.gmk    Fri Jan 24 11:03:15 2014 -0800
+++ b/make/Setup.gmk    Fri Jan 24 13:41:24 2014 -0800
@@ -27,7 +27,7 @@

  # To build with all warnings enabled, do the following:
  # make JAVAC_WARNINGS="-Xlint:all -Xmaxwarns 10000"
-JAVAC_WARNINGS := 
-Xlint:-unchecked,-deprecation,-overrides,auxiliaryclass,classfile,dep-ann,divzero,empty,overloads,static,try,varargs 
-Werror
+JAVAC_WARNINGS := 
-Xlint:-unchecked,-deprecation,-overrides,auxiliaryclass,cast,classfile,dep-ann,divzero,empty,overloads,static,try,varargs 
-Werror

  # Any java code executed during a JDK build to build other parts of 
the JDK must be
  # executed by the bootstrap JDK (probably with -Xbootclasspath/p: ) 
and for this

Thanks,

-Joe