[ASan][OSX] Fix the incorrect malloc_create_zone() implementation that led to out-of-bounds mprotect()s
(https://code.google.com/p/address-sanitizer/issues/detail?id=203)
Add a test.



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@185138 91177308-0d34-0410-b5e6-96231b3b80d8