[OpenCL] Set KHR extensions minimum version to OpenCL 1.0 (#175120)
Motivation is similar to 25cfdaa4e9dc. Their spec don't specify a
required OpenCL version. Targets may expose them before OpenCL 1.2.
Set KHR extensions (depth images, mipmaps, subgroups, kernel clock, dot
product, ext_float_atomics, extended_bit_ops, cles_khr_int64) to
availability 1.0.
Changes to opencl-c.h:
* Relax header and test guards to allow extension macros whenever any
OpenCL C version is defined.
* Relax cl_khr_depth_images guard to allow cl_khr_depth_images, OpenCL
C++, or OpenCL C 2.0+, since image2d_depth_t and image2d_array_depth_t
types require that coverage.
* Guard image1d_t, image1d_array_t and image2d_array_t types with OpenCL
C++ or OpenCL C 1.2+ to match with OpenCL C spec.
Relates to https://github.com/KhronosGroup/OpenCL-CTS/pull/2376.