Link for AMD-APP-SDK-v.2.8
Cleanup it a bit.
AMD SDK examples need libSDL, mention it in the README files.
AMD examples: Added info of the 'cmake' requirement and the 'prepare-examples' step.
Implement CL_PROGRAM_NUM_KERNELS in clGetProgramInfo.
Implemented CL_PROGRAM_KERNEL_NAMES.

Also works when pocl_llvm_get_kernel_names returns 0,
but with empty kernel file that function segfaults instead.