This is a fundamentally simplified reimplementation of #5317
by @shuujii
Instead of having array of `struct iv_elem`, we have sequences of keys
and values packed in single chunk of malloc'ed memory. We don't have to
worry about gaps from alignment, especially on 64 bit architecture,
where `sizeof(struct iv_elem)` probably consumes 16 bytes, but
`sizeof(mrb_sym)+sizeof(mrb_value)` is 12 bytes.
In addition, this change could improve memory access locality.
close#5317
Make "N for M" into the form "given N, expected M".
As I worked, I noticed that the `argnum_error()` function had a part to include the method name in the message.
I think this part is no longer needed by https://github.com/mruby/mruby/pull/5394.
- Before this patch
```console
% bin/mruby -e '[1, 2, 3].each 0'
trace (most recent call last):
[1] -e:1
-e:1:in each: 'each': wrong number of arguments (1 for 0) (ArgumentError)
```
- After this patch
```console
% bin/mruby -e '[1, 2, 3].each 0'
trace (most recent call last):
[1] -e:1
-e:1:in each: wrong number of arguments (given 1, expected 0) (ArgumentError)
```
If the preprocessor check part is only `__clang__`, CI's such as `Ubuntu-2004-clang` will fail to compile.
This is why we limited the addition to FreeBSD and OpenBSD, which have `clang++` in their base systems.
DragonFly BSD and NetBSD have GCC built into their base systems, so nothing is changed.
The `__id__` method implemented in the C function has `MRB_ARGS_NONE()` specified, but it is also effective in the following cases.
```ruby
p nil.__id__ opts: 1 rescue p :a
p nil.method(:__id__).call 1 rescue p :b
p nil.method(:__id__).call opts: 1 rescue p :c
p nil.method(:__id__).to_proc.call 1 rescue p :d
p nil.method(:__id__).to_proc.call opts: 1 rescue p :e
p nil.method(:__id__).unbind.bind_call nil, 1 rescue p :f
p nil.method(:__id__).unbind.bind_call nil, opts: 1 rescue p :g
p nil.__send__ :__id__, 1 rescue p :h
p nil.__send__ :__id__, opts: 1 rescue p :i
```
After applying this patch, all items will output symbols in the same way as CRuby.
For this purpose, add `MRB_PROC_NOARG` to `struct RProc::flags`.
Calling the `Method#{parameters,source_location}` method on a static `Proc` object resulted in `SIGSEGV`.
The trigger is https://github.com/mruby/mruby/pull/5402.
The original implementation of the `Method#{parameters,source_location}` method was to temporarily rewrite the object and then call the method of the same name in `Proc`.
Rewriting of objects placed in the ROM section by #5402 above is prohibited by hardware such as the CPU.
This caused a `SIGSEGV`.
If a splat argument was passed, it could write out of range on the VM stack.
```console
% bin/mruby -e 'def m(*args, **opts, &blk) p [args, opts, blk] end; m(*%w(X Y Z), r: 1, g: 2, b: 3) {}'
[["X", "Y", "Z"], {}, #<Proc:0x80077d7d0>]
```
Yukihiro "Matz" Matsumoto