Disallow using function parameters in extended asm inputs or outputs in naked functions (PR21178)

Clang won't emit any prologues for such functions, so it would assert trying to
codegen the parameter references.

This patch makes Clang check the extended asm inputs and outputs for
references to function parameters.

Differential Revision: http://reviews.llvm.org/D5640

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@219272 91177308-0d34-0410-b5e6-96231b3b80d8