Do simple keyword replacements, commenting out and translation at the end

This allows the main part of the preprocessor to work with source
in the actual input format and not have to look for directives
in their translated form (which can be different depending on the
target).
Support running the preprocessor only, for deps
Support running the preprocessor only, for deps
Add a script for comparing the disasm of all asm files
Don't convert add to add.w when using gas
Don't remove dots for .Llocal symbols when using gas
Don't do literal restructuring when using gas