* AstGen: fix not emitting `struct_init_empty` when an explicit type is
present in struct initialization syntax.
* AstGen: these two syntaxes now lower to identical ZIR:
- `var a = A{ .b = c };`
- `var a = @as(A, .{ .b = c });`
* Zir: clarify `auto_enum_tag` in the doc comments.
* LLVM Backend: fix lowering of function return types when the type has
0 bits.
Locals are not allowed to shadow declarations, but declarations are
allowed to shadow each other, as long as there are no ambiguous
references.
closes#678
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.
