also fixes ADD and SUB to use U modifier

Along with implementations of common instructions along the way

This tries to fix a data race where we'd wait forever for the GPU.

This is enabled by an extension instead of the capability.

Workaround bug on Nvidia's OpenGL SPIR-V compiler when using unsigned
texture offsets.

Workaround more bugs on Nvidia's OpenGL SPIR-V compiler.

Worksaround a bug on Nvidia's OpenGL SPIR-V compiler where names are
used for name matching.