i#678: implement optimizations from Dr. Memory in drwrap, part 4 + if there is no post-call hook, avoid cost of flushing retaddr
i#678: implement optimizations from Dr. Memory in drwrap, part 4
+ if there is no post-call hook, avoid cost of flushing retaddr

git-svn-id: ed337ca7cdb08c0ba29d8fe58632bb7686892c2d@1260 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6

rnk/dynamorio,rnk/dynamorio,rnk/dynamorio,rnk/dynamorio,rnk/dynamorio