Instead of doing everything at once which is a hopelessly large task,
this introduces a piecemeal transition that can be done in small
increments at a time.
This is a minimal changeset that keeps the compiler compiling. It only
uses the InternPool for a small set of types.
Behavior tests are not passing.
Air.Inst.Ref and Zir.Inst.Ref are separated into different enums but
compile-time verified to have the same fields in the same order.
The large set of changes is mainly to deal with the fact that most Type
and Value methods now require a Module to be passed in, so that the
InternPool object can be accessed.
* move `ptrBitWidth` from Arch to Target since it needs to know about the abi
* double isn't always 8 bits
* AVR uses 1-byte alignment for everything in GCC
Many `Type`s can correspond to the same `CType`, so this reduces the
number of used locals by 27760 when compiling only-c.
Also, disabled some tests that were only passing by accident and
shouldn't really be considered working.
This requires manual defines before C99 which may not have stdint.h.
Also have update-zig1 leave a copy of lib/zig.h in stage1/zig.h, which
allows lib/zig.h to be updated without needing to update zig1.wasm.
Note that since the object already existed with the exact same contents,
this completely avoids repo bloat due to zig.h changes.
