Reapply 272328 and 272329 as a single patch.

[cpu-detection] [amdfam10] Return barcelona, and amdfam10 for all other
subtypes. Address Bug 28067.

Along with the refactoring of Host.cpp, getHostCPUName() was modified to
return more precise types for CPUs in amdfam10.
However, callers of getHostCPUName() do string matching on type, so this
cannot be modified.
Currently there is support in the x86 backend for barcelona.
For all other subtypes the assumed return value is amdfam10.

Fix: getHostCPUName() returns barcelona subtype and amdfam10 for all
others. This can be extended further when support for the other subtypes
is added.

Differential revision: http://reviews.llvm.org/D21193

llvm-svn: 272333