j6libc.py was initially made for libc to generate stdint.h, but it gained a few things that aren't libc-specific. Move it to a package and split the int-types-specific code into codegen.int_types.
j6libc.py was initially made for libc to generate stdint.h, but it gained a few things that aren't libc-specific. Move it to a package and split the int-types-specific code into codegen.int_types.