IRgen/ObjC: Correctly construct the function info for variadic message sends.

This fixes some bad -O0 codegen and the unnecessary clearing of al on entry to objc_msgSend for most message sends.

<rdar://problem/7102824> [irgen] unnecessary xorb on calls to objc_msgSend on x86_64

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82118 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed