Allow compilation on OpenCL 1.1 headers

Wrap enqueueFillBuffer and 1.2 platform detection into ifdefs for
CL_VERSION_1_2, which is only available when usin 1.2 headers (or
later).
Merge branch 'runtime-ocl11' of git://github.com/Oblomov/vramfs into Oblomov-runtime-ocl11

Conflicts:
	src/memory.cpp
Merge branch 'Oblomov-runtime-ocl11'