* fixed FLOAT_16/half image and framebuffer handling (this is uglier and more cumbersome than one would think, since no opencl implementation supports cl_khr_fp16 and there are severe restrictions on the half type in OpenCL 1.2 core)
 * -> removed old half* workaround, added new oclr_half* typedefs (these are empty, but correctly aligned structs) which are used instead of half* everywhere now (-> works on all opencl platforms)
 * added image_support_template_fp16.h that is specific to half type image handling (sadly necessary, since all half type reads must be done via vload_half* and must always use a half pointer, because there are no half vector types)
 * when querrying the opencl device info, also extract and store the devices opencl c version
 * don't specify the "-cl-std" build option any more, this will default to the max supported device OpenCL C version automatically (as per spec)
 * only enable OpenCL 1.0/1.1 extensions that are now part of OpenCL 1.2 core when compiling with OpenCL C < 1.2
 * fixed framebuffer copy in pipeline (+image header offset); note that image/framebuffer reading/writing still needs fixing in that regard (next commit)
 * fixed install script for mingw
 * updated simple_shader_fs to use a framebufer