-Refactored ARMTargetInfo in order to use the API of TargetParser

 for extracting target specific information.
-Patches commit r241343: case 'armv7l' was unhandled in
 ARMTargetInfo::getCPUAttr(), and thus it was returning invalid
 characters for macro definition.

Change-Id: I1a0972e5ff5529cd17376c6562047bab8b4da32c
Phabricator: http://reviews.llvm.org/D10839
llvm-svn: 242514