unique_ptrify Driver Action handling

It hits a limit when we reach ActionList, which is used for dynamic
conditional ownership, so we lose type safety there.

This did expose at least one caller "lying" about ownership (passing
ownership to an Action, then updating the Action to specify that it
doesn't actually own the thing that was passed) - changing this to
unique_ptr just makes that oddity more obvious.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@216713 91177308-0d34-0410-b5e6-96231b3b80d8
CodeGen: Don't completely mess-up optimized atomic libcalls

Summary:
We did a great job getting this wrong:
- We messed up which LLVM IR types to use for arguments and return values.
  The optimized libcalls use integer types for values.

  Clang attempted to use the IR type which corresponds to the value
  passed in instead of using an appropriately sized integer type.  This
  would result in violations of the ABI for, as an example, floating
  point types.
- We didn't bother recording the result of the atomic libcall in the
  destination memory.

Instead, call the functions with arguments matching the type of the
libcall prototype's parameters.

This fixes PR20780.

Differential Revision: http://reviews.llvm.org/D5098

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@216714 91177308-0d34-0410-b5e6-96231b3b80d8