Many of the files have using std::<foo> statements in them, but then the
use of <foo> will be inconsistently std::<foo> or <foo> scattered
through the file. This CL removes all of the using statements and
updates the code to have the required std:: prefix.
Add SPV_ENV_WEBGPU_0 for work-in-progress WebGPU.
val: Disallow OpUndef in WebGPU env
Silence unused variable warnings when !defined(SPIRV_EFFCE)
Limit visibility of validate_instruction.cpp's symbols
Only InstructionPass needs to be visible so all other functions are put
in an anonymous namespace inside the libspirv namespace.