[PATCH] [Msan] Generalize mapping facilities to add FreeBSD support

[Evgeniy Stepanov]

LGTM

================
Comment at: lib/msan/msan.h:36
@@ +35,3 @@
+5900 0000 0000 - 5fff ffff ffff: Bad3
+6000 0000 0000 - 7fff ffff ffff: High memory: traces, heap, modules and main thread stack
+
----------------
There are no "traces" in MSan.

http://reviews.llvm.org/D6387