On PowerPC64, integer arguments and return values need to be sign- or

On PowerPC64, integer arguments and return values need to be sign- or
zero-extended to 64 bits.  This information is currently provided to
the back end by setting "signext" or "zeroext" attributes.  However,
this is done only for integer types *smaller* than i32, not for i32
itself.  This causes clang to generate code violating the ABI, which
results in a failure of the tramp3d-v4 test case (due to calling a
system library routine without ABI-required extension).

This patch implements custom versions of classifyArgumentType and
classifyReturnType for PPC64_SVR4_ABIInfo, which are the same as the
default versions except that they also classify "int" and "unsigned int"
as types needing extending.  This fixed tramp3d-v4 on PowerPC64.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167393 91177308-0d34-0410-b5e6-96231b3b80d8