PrimeSense support + some compatibility-related changes

Hey,

so I ended up using kernel_fpu_begin/kernel_fpu_end to enclose the floating-point operations in the kernel space. I "stress-tested" it, having two stupid programs running on both of my cores and doing  floating point calculations with checking while plugging in the cameras and checking the calculations there.
I made some compatibility-related changes as I wrote, since I'm on Ubuntu 14.04 and with kernel 3.13-something and your code was adapted to a somewhat newer versions.

Let me know if anything needs correction.