fixes issue 1065
fixes issue 1065

Change the shift used for the sentinel to accomodate small integers like
the SIG_IGN seen in python.  Add release build fallback of skipping if
it does match.

SVN-Revision: 1104

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