Add batch file that builds and executes all GPR tests.

Removed bad format test to fix gpr_string_test.
Also took care of some of the MS compiler warnings when compiling gpr_test_util.
	Change on 2014/12/11 by jtattermusch <jtattermusch@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81900639