Implemented clCreateImage* and clEnqueue{Read,Write,Copy}Image.

Enabled image support in clGetDeviceInfo. Currently not supporting
image arrays and buffers, or packed image formats.
Implemented write_imagef and get_image_* builtins.
Implemented write_imagei and write_imageui builtins.
Implemented read_imagef with sampler for CL_FILTER_NEAREST.
Fixed exclusion of arrays and buffers in clGetSupportedImageFrmats.
Implemented CL_FILTER_LINEAR for read_imagef.
Implemented sampler versions of read_image{i,ui}.
Implemented sampler-less read functions.
Implemented clGetImageInfo.
Implemented clEnqueueMapImage.
Implemented clEnqueueFillImage.
Added __IMAGE_SUPPORT__ definition to clc.h as temporary workaround.
Implemented clEnqueueCopy{Buffer,Image}To{Image,Buffer}.
Implemented clGetSamplerInfo.
Enabled image arrays in runtime.
Implemented get_image_array_size builtin.
Implemented reading and writing for image arrays.
Implemented 1D image buffers.