i#893 Rtl heap replacement fixes + fix realloc of pre-us + tweak comments
i#893 Rtl heap replacement fixes
+ fix realloc of pre-us
+ tweak comments

git-svn-id: fe3cd4388a6e5a968b09397a3d721fe124e8117a@930 5b54908e-ead4-fc18-b48a-0285e6dbc711

rnk/drmemory,rnk/drmemory,rnk/drmemory,rnk/drmemory