[CUDA] Detect and link with CUDA's libdevice bitcode library.

- added detection of libdevice bitcode file and API to find one appropriate for the GPU we're compiling for.
- pass additional cc1 options for linking with detected libdevice bitcode
- added -nocudalib to prevent automatic linking with libdevice
- added test cases to verify new functionality

Differential Revision: http://reviews.llvm.org/D14556

llvm-svn: 253387