i#1079 front-end lib: add MacOS implementation of drfront_is_64bit_app().
i#1079 front-end lib: add MacOS implementation of drfront_is_64bit_app().

Also simplifies the bit testing in drfront_access().

SVN-Revision: 2607

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