[py3] Teach the CMake build to reject Python versions older than 2.7.
Continue to require Python 2 however as recent experiments suggest
LLDB's build requires it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224948 91177308-0d34-0410-b5e6-96231b3b80d8
[Hexagon] Renaming old multiclass for removal.  Adding post-increment store classes and instruction defs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224949 91177308-0d34-0410-b5e6-96231b3b80d8
Convert test to FileCheck. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224950 91177308-0d34-0410-b5e6-96231b3b80d8