[SimplifyLibCalls] Library call simplification doen't work if the call site 
isn't using the default calling convention.  However, if the transformation is
from a call to inline IR, then the calling convention doesn't matter.
rdar://13157990

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174724 91177308-0d34-0410-b5e6-96231b3b80d8