Show message box on assert only if USE_MSBOX is true; reviewed as http://codereview.appspot.com/1668044
Show message box on assert only if USE_MSBOX is true; reviewed as http://codereview.appspot.com/1668044

SVN-Revision: 19

code4bones/drmemory,sigma-random/drmemory,sigma-random/drmemory,sigma-random/drmemory,LohithBlaze/drmemory,code4bones/drmemory,code4bones/drmemory,LohithBlaze/drmemory,code4bones/drmemory,code4bones/drmemory,sigma-random/drmemory,LohithBlaze/drmemory,LohithBlaze/drmemory,LohithBlaze/drmemory,sigma-random/drmemory