When a signed integer's bitsize is not 32 or 64, but the given
bitsize and wanted bitsize are either both represented by Wasm's i32
or i64, we must either sign extend or wrap the integer.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
* Identify the ones that are passing and stop skipping them.
* Flatten out the main behavior.zig file and have each individual test
disable itself if it is not passing.
- This implements the float_to_int AIR instruction.
- Lowering a decl_ref to a slice was previously assumed to contain a pointer
to a slice, rather than an array. This is now fixed, making `@src()` work as well.
- Some preliminary work on 128bit integers have been done to find out what needs to be done
to implement 128bit arithmetic.
