Add intrinsics for OpenCL C 2.0+ linear work-item ID functions

Extend experimental implementation comparison

Remove some unused/deprecated instrinsic functions

Add functions for extended precision float arithmetic and improve expN implementations

Add test program to quickly compare different implementations of math functions

Adds SPIR mangling for all async_work_group(_strided)_copy functions

Greatly improve logX accuracies and some other improvements

Fixes geometric functions for extreme values and adds some OpenCL C 3.0 functions

Adds support for subnormal values for (i)logb and ceil

Implements correct algorithm for (r)sqrt

Implements edge-case behavior for some math functions

Adds basic support for OpenCL C functions with __generic address space

Implements and fixes some (u)long functionality

Some fixes and improvements

Removes some declarations and aliases not supported by SPIRV-LLVM-Translator