- String#__lines
- Array#__ary_eq
- Array#__ary_cmp
- Hash#__delete
- Kernel#__case_eqq
- Integer#__coerce_step_counter

Mrbgem gem_init.c: add headers for irep loading when cdump is disabled, but presym is enabled

Do not include `stdint.h` before `mruby.h`

When `disable_cdump` is declared on a Mrbgem spec, the procedure for
loading MRuby code from the gem's `mrblib` directory is slightly
different; instead of loading the mrblib code as a Proc built from the
compiled irep, the compiled irep is loaded directly. The header files
`mruby.h` and `mruby/proc.h` are needed only when the irep is loaded
directly. They are currently included only when presym is disabled, they
should be included whenever either presym is disabled *or* when
`disable_cdump` is called. The `cdump?` predicate method happens to
return true in either case (presym disabled *or* cdump disabled), so
this change should be safe.

A change in `load.c` is left uncommitted.

That means it's a method not to be included in the backtrace, for
example `raise`.

It uses BER number compression of delta of instruction positions and line
numbers. BER compression is a variable length number representation.

* `mrb_debug_line_ary`: array of line numbers represented in `uint16_t`.
  `[lineno, lineno, ...]`

* `mrb_debug_line_flat_map`: array of `mrb_irep_debug_info_line`, which
  is `struct {uint32_t pos; uint16_t lineno}`, for each line.

* `mrb_debug_line_packed_map` [new]: sequence of BER compressed 2
  numbers, `pos_delta, lineno_delta`. Deltas are differences from
  previous values (starting `0`). `line_entry_counts` represents total
  length of a packed map string for this type.

Add information on yamllint as comments

Style the CONTRIBUTING guide

Merge branch 'mrb_debug_strdup-and-strndup' of https://github.com/cremno/mruby into cremno-mrb_debug_strdup-and-strndup

To be compatible with CRuby.

- `Lit` -> `Pool`
- `SEQ` -> `Irep`

The code generator no longer need to emit `OP_LOADSYM` after `OP_DEF`.
`doc/opcode.md` is also updated.

This reverts commit fd10c723.

I thought it was OK to restrict index value within 1 byte, but in some
cases index value could be 16 bits (2 bytes). I had several ideas to
address the issue, but reverting `fd10c723` is the easiest way. The
biggest reason is `mruby/c` still supports `OP_EXT[123]`, so that they
don't need any additional work.

Drop unnecessary upper procs linked from class/module/def syntax

Avoid warnings with `ruby -cw`

```console
% for rb in `git ls-files '*/mrblib/*.rb' 'mrblib'`; do ruby30 -cw $rb > /dev/null; done
mrbgems/mruby-array-ext/mrblib/array.rb:389: warning: assigned but unused variable - ary
mrbgems/mruby-array-ext/mrblib/array.rb:663: warning: assigned but unused variable - len
mrbgems/mruby-hash-ext/mrblib/hash.rb:119: warning: possibly useless use of a variable in void context
mrbgems/mruby-hash-ext/mrblib/hash.rb:259: warning: assigned but unused variable - keys
mrbgems/mruby-io/mrblib/io.rb:229: warning: literal in condition
mrbgems/mruby-io/mrblib/io.rb:280: warning: literal in condition
mrbgems/mruby-string-ext/mrblib/string.rb:347: warning: assigned but unused variable - len
mrbgems/mruby-toplevel-ext/mrblib/toplevel.rb:2: warning: parentheses after method name is interpreted as an argument list, not a decomposed argument
```

It does not need to hold an anonymous proc for constant search.
Also, this change can be expected to cause an anonymous proc to be GC'd.

This is useful for metaprogramming that makes heavy use of the `class`/`module`/`def` syntax in the `class_eval`/`eval` method.

Example:

- code

  ```ruby
  p ObjectSpace.count_objects

  String.class_eval do
    def a
    end
  end

  p ObjectSpace.count_objects

  String.class_eval do
    eval <<~CODE
      def b
      end
    CODE
  end

  p ObjectSpace.count_objects
  ```

- result of building mruby-head (d63c0df6) with `build_config/default.rb`

  ```
  {:TOTAL=>1024, :FREE=>262, :T_PROC=>495, :T_ENV=>61, ...}
  {:TOTAL=>1024, :FREE=>259, :T_PROC=>497, :T_ENV=>62, ...}
  {:TOTAL=>1024, :FREE=>255, :T_PROC=>500, :T_ENV=>63, ...}
  ```

- result of building mruby with this patch and `build_config/default.rb`

  ```
  {:TOTAL=>1024, :FREE=>264, :T_PROC=>494, :T_ENV=>60, ...}
  {:TOTAL=>1024, :FREE=>262, :T_PROC=>495, :T_ENV=>61, ...}
  {:TOTAL=>1024, :FREE=>261, :T_PROC=>496, :T_ENV=>61, ...}
  ```

Fixed finding variables from `proc` in `binding.eval` failed