Wrapped some variables to quotation marks to prevent breakage if there is spaces in path name
Disabled invalid compile check for now and fixed invalid /dev/null reference
Ignored some cmake checks for now if compiling in windows.
Removed stdlib deps from cmake test.

In windows clang might not have standard c libs and pocl does not need them either since clang is used just to compile OpenCL. Also fixed some other windows compatibilities and set up install path where complete lib should be installed. In windows there is no /etc/opencl/vendors, but ref to .icd s written to windows registry.
Fixed some alignments to cross platform compatible and disabled pthreads driver for now.
Silenced few errors from headers.
Fixed unistd header alternative for windows.
Fixed few more headers / GCC pragmas for VC++
Added missing include directories to Cmake files and fixed some preprocessor macros.
Fixed more llvm version checks to be VC++ compatible.
Fixed some cl_float .x .y .z .w refs to be windows compatible.
Fixed some more cl_float .s0-f refs to be windows compatible.
Disabled cl_platform.h fixes since vc++ does not support include next.