Remove a trailing space in `MRUBY_DESCRIPTION`

Remove unnecessary type `mrb_hash_value`

The type `mrb_hash_value` is no longer used by the segmented list
implementation (ref e8dcfe17 and e65d4264).

Print missing `:` before newline in `mrb_parser_dump`

Allow rethrowing `MRB_TT_BREAK`

Restore GC arena frequently

Remove unnecessary assignments

Add an annotation about the return value

The return value from `mrb_delete_key` needs to be protected from GC in
some cases.

Remove unused node type in `codegen()`

Simplify arguments check in `String#rindex`

Also fix document about type of the first argument.

Use type predicate macros instead of `mrb_type` if possible

For efficiency with `MRB_WORD_BOXING` (implement type predicate macros for
all `enum mrb_vtype`).

The following two may be different:
* `%d` for `int`
* `%i` for `mrb_int`

Use inttypes for `snprintf()`

Keep the type of `posarg` consistent

Remove `MRB_TT_HAS_BASIC` macro

Fix `MRB_WITHOUT_FLOAT` reversal; fix #4598

Add "fall through"

* mrb_sym2name -> mrb_sym_name
* mrb_sym2name_len -> mrb_sym_name_len
* mrb_sym2str -> mrb_sym_str

Match the type with the caller and related functions.

The value of `MRB_TT_HAS_BASIC` is meaningless because `MRB_TT_HAS_BASIC` is
no longer used with `MRB_WORD_BOXING` at b2c3d88f.

`Exception#initialize` should not allow two or more arguments

Fix `Fixnum` overflow test in `Integer#<<` test

- Skip when `MRB_WITHOUT_FLOAT` is defined.
- Make `Fixnum` overflow even when `MRB_INT64` is defined.