Generalize target weirdness handling having proper layering in mind:
 1. Add helper class for sema checks for target attributes
 2. Add helper class for codegen of target attributes

As a proof-of-concept - implement msp430's 'interrupt' attribute.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@93118 91177308-0d34-0410-b5e6-96231b3b80d8
14 files changed