i#678: implements DrMemi#460.B optimization: switch to rwlock for post_call_lookup
i#678: implements DrMemi#460.B optimization:
switch to rwlock for post_call_lookup

SVN-Revision: 1255

bl4ckic3/dynamorio,sigma-random/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,daksunt/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio,daksunt/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio