`Float::NAN/0` should be `Float::NAN`; ref a0b3378b

#### Before this patch:

```console
$ bin/mruby -e 'p(Float::NAN/0)'
Infinity
```

#### After this patch (same as Ruby):

```console
$ bin/mruby -e 'p(Float::NAN/0)'
NaN
```

It used to be return the default value if available, but it should
ignore the default value for behavior consistency. CRuby will adopt
this behavior too in the future. [ruby-bugs:16908]

Fix typo in `AUTHORS` [ci skip]

The issue was reported by @shuujii

Add new pool value type `IREP_TT_BIGINT` and generate integer overflow
error in the VM. In the future, `mruby` will support `Bignum` for
integers bigger than `mrb_int` (probably using `mpz`).

bug(presym): Fix mrb_cmp declaration of <=> symbol for funcall

chore: upgrade markdownlint GitHub Action node version to 14

chore: fix grammar

Upgrade to  markdownlint-cli version 0.27.1

`gmtime_r` detection logic was too strict.

chore: fix spelling

Merge mruby 3.0.0

Fix load 64-bit integer from mrb format; fix #5369

Update minimal build configuration [ci skip]

Remove unused `mrblib/init_mrblib.c`