Move library call prototype attribute inference to functionattrs

The simplify-libcalls pass implemented a doInitialization hook to infer
function prototype attributes for well-known functions.  Given that the
simplify-libcalls pass is going away *and* that the functionattrs pass
is already in place to deduce function attributes, I am moving this logic
to the functionattrs pass.  This approach was discussed during patch
review:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20121126/157465.html.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177619 91177308-0d34-0410-b5e6-96231b3b80d8