previous implementation was not thread/stream safe, since it used constant
memory

new implementation doesn't use any global objects, so it is thread/stream safe

Add GPU models in seperate folder, only old models are supported and they were replaced to make the CPU interface work.
This solves the undesired consequence of breaking the GPU interface.

move hog::set_up_constants from constructor to compute method

if user changed CUDA device between constructor and computation,
some variables were uninitialized

This avoids violation of possible future CMake policy checks
regarding reserved/read-only variables.

Everything else depends on it, after all.

Which also happens to align the non-Debian specific variables
with the ones used by upstream CMake.

It's pretty much a simplified copy of the Linux script, lacking fancy colors.
Also, I had to drop Python testing, because it's not easy to pass the Python
module location to the script, and I have no pressing need to run the Python
tests at the moment.

The use of built-in CMAKE_CURRENT_LIST_DIR requires at least
CMake 2.8.3. This fix properly defines the variable to allow its
use in versions < 2.8.3 as well.

Fixes issue #4205.