[compiler-rt] Fix sanitizer memory allocator on win64.

Summary:
This patch is fixing unittests for sanitizer memory allocator.

There was two issues:
  1) The VirtualAlloc can't reserve twice a memory range.
     The memory space used by the SizeClass allocator is reserved
     with NoAccess and pages are commited on demand (using MmapFixedOrDie).

  2) The address space is allocated using two VirtualAlloc calls. The first one
     for the memory space, the second one for the AdditionnalSpace (after).

     On windows, they need to be freed separately.

Reviewers: rnk

Subscribers: llvm-commits, wang0109, kubabrecka, chrisha

Differential Revision: http://reviews.llvm.org/D21900

llvm-svn: 274772