CodeGen: __uuidof should work even with an incomplete _GUID type

Summary:
We would crash in CodeGen::CodeGenModule::EmitUuidofInitializer
because our attempt to enter CodeGen::CodeGenModule::EmitConstantValue
will be foiled: the type of the constant value is incomplete.

Instead, create an unnamed type with the proper layout on all platforms.
Punt the problem of wrongly defined struct _GUID types to the user.
(It's impossible because the TU may never get to see the type and thus
we can't verify that it is suitable.)

This fixes PR16856.

Reviewers: rsmith, rnk, thakis

Reviewed By: rnk

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1375

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188481 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: Revert change to the return type of createRecordFwdDecl

It still does only return DICompositeType, but I've no need to make that
change right now.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188482 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: Unify & optimize the lazy addition of record types

Rather than going through the whole getOrCreateType machinery to
manifest a type, cut straight to the implementation because we know we
have to do work.

While the previous implementation was sufficient for the two cases
(completeness and required completeness) we have already (the general
machinery could inspect the type for those attributes & go down the full
definition path), a pending change (to emit info for types when we emit
their vtables) won't have that luxury & we'll need to force the creation
rather than relying on the general purpose routine.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188486 91177308-0d34-0410-b5e6-96231b3b80d8
make arm-use-movt available for all ARM

This updates clang according to a pending patch for llvm to
rename of the -arm-darwin-use-movt to arm-use-movt to make
it available for all of ARM.

note: please apply this close to the llvm change.

Patch by Jeroen Hofstee.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188488 91177308-0d34-0410-b5e6-96231b3b80d8