InstrProf: Indicate pointer size in raw profile

Since the profile can come from 32-bit machines, the reader needs to
check the pointer size.  Change the magic number to facilitate this.

<rdar://problem/16400648>

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@204556 91177308-0d34-0410-b5e6-96231b3b80d8