Merge LLVM r202188:

  Debug info: Support variadic functions.
  Variadic functions have an unspecified parameter tag after the last
  argument. In IR this is represented as an unspecified parameter in the
  subroutine type.

  Paired commit with CFE r202185.

  rdar://problem/13690847

  This re-applies r202184 + a bugfix in DwarfDebug's argument handling.

This merge includes a change to use the LLVM 3.4 API in
lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp:

DwarfUnit -> CompileUnit

Sponsored by:       DARPA, AFRL
Merge Clang r202185:

  Debug info: Generate debug info for variadic functions.
  Paired commit with LLVM.

  rdar://problem/13690847

This merege includes changes to use the Clang 3.4 API (revisions
199686 and 200082) in lib/CodeGen/CGDebugInfo.cpp:

getParamType  -> getArgType
getNumParams  -> getNumArgs
getReturnType -> getResultType

Sponsored by:	DARPA, AFRL
Add patches corresponding to r264826 and r264827