Fix confused definitions of pre/post increment/decrement (#827)
Fix confused definitions of pre/post increment/decrement (#827)

* Fix confused definitions of pre/post increment/decrement

We somehow have been compiling `++i` as `i++` (and vice versa) for a long time without noticing.

This change fixes the implementation of these pseudo-ops in IR codegen, and adds a comment to explain the rationale for why their definitions should be what they are.

* fixup: typo

csyonghe/slang,csyonghe/slang,csyonghe/slang,shader-slang/slang,shader-slang/slang,shader-slang/slang