clang: add -f{no-,}integrate-as as consistent parameters

The integrated assembler is a feature.  This makes the new flags the default
option, and the previous versions aliases.  Ideally, at some point the aliases
would be entirely removed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201963 91177308-0d34-0410-b5e6-96231b3b80d8