* CLI: `-target [name]` instead of `--target-*` args.
This matches clang's API.
* `builtin.Environ` renamed to `builtin.Abi`
- likewise `builtin.environ` renamed to `builtin.abi`
* stop hiding the concept of sub-arch. closes#1526
* `zig targets` only shows available targets. closes#438
* include all targets in readme, even those that don't
print with `zig targets` but note they are Tier 4
* refactor target.cpp and make the naming conventions
more consistent
* introduce the concept of a "default C ABI" for a given
OS/Arch combo. As a rule of thumb, if the system compiler
is clang or gcc then the default C ABI is the gnu ABI.
* codegen: LLVMConstInlineAsm is deprecated.
* codegen: replace commas in asm constraint strings by pipes as required by LLVM.
* ir: enforce usage of '=' constraint modifier for inline assembly outputs.
Others are not currently supported and this was just asserted alter in `ir_render_asm`.
* asm: forbid comptime_int/floats as inputs in favor of explicitely sized constants.
Fixes a crash due to comptime_int/floats having no type_ref.
* asm: handle inputs with integers of <8 or non power of 2 bitsize.
We widen them to the next highest power of two.
