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
* remove `LoweringError` error set from `Emit.zig` - it actually
was less than helpful; it's better to either not throw an error
since there can be instructions with mismatching operand sizes
such as `movsx` or assert on a by instruction-basis. Currently,
let's just pass through and see how we fare.
* when moving integers into registers, check for signedness and move
with zero- or sign-extension if source operand is smaller than 8
bytes. The destination operand is always assumed to be full-width,
i.e., 8 bytes.
* clean up `airTrunc` a little to match the rest of CodeGen inst
implementations.
Conflicts:
* doc/langref.html.in
* lib/std/enums.zig
* lib/std/fmt.zig
* lib/std/hash/auto_hash.zig
* lib/std/math.zig
* lib/std/mem.zig
* lib/std/meta.zig
* test/behavior/alignof.zig
* test/behavior/bitcast.zig
* test/behavior/bugs/1421.zig
* test/behavior/cast.zig
* test/behavior/ptrcast.zig
* test/behavior/type_info.zig
* test/behavior/vector.zig
Master branch added `try` to a bunch of testing function calls, and some
lines also had changed how to refer to the native architecture and other
`@import("builtin")` stuff.
