Fix mangled name of method with ns_consumed parameters.

When a function/method use a parameter with "ns_consumed" attribute,
ensure that the mangled name is the same whether -fobjc-arc is used
or not.

Since "ns_consumed" attribute is generally used to inform ARC that
a function/method does sink the reference, it mean it is usually
implemented in a compilation unit compiled without -fobjc-arc but
used form a compilation unit compiled with it.

Originally found while trying to use "ns_consumed" attribute in an
Objective-C++ file in Chromium (http://crbug.com/599980) where it
caused a linker error.

Regression introduced by revision 262278 (previously the attribute
was incorrectly not part of the mangled name).

Patch from Sylvain Defresne <sdefresne@chromium.org>!
http://reviews.llvm.org/D20113

llvm-svn: 270702