[CUDA] Copy host builtin types to NVPTXTargetInfo.

Summary:
Host and device types must match, otherwise when we pass values back and
forth between the host and device, we will get the wrong result.

This patch makes NVPTXTargetInfo inherit most of its type information
from the host's target info.

Reviewers: rsmith

Subscribers: cfe-commits, jhen, tra

Differential Revision: http://reviews.llvm.org/D19346

llvm-svn: 268131