New mutator for bcmath

[majkel89]

This PR:

• Adds BCMath extension mutator (MBString)
• Covered by tests
• Doc PR: #658 BCMath mutator docs site#125

Fixes #658

Supported functions:

• bcadd($a, $b, $mod) -> (string) ($a + $b)
• bcdiv($a, $b, $mod) -> (string) ($a / $b)
• bcmod($a, $b, $mod) -> (string) ($a % $b)
• bcmul($a, $b, $mod) -> (string) ($a * $b)
• bcpow($a, $b, $mod) -> (string) ($a ** $b)
• bcsub($a, $b, $mod) -> (string) ($a - $b)
• bcsqrt($a, $mod) -> (string) sqrt($a)
• bcpowmod($a, $b, $c, $mod) -> (string) (pow($a, $b) % $c)
• bccomp($a, $b, $mod) -> $a <=> $b

New profile @extensions created to hold this mutator. It is on by default.

Configuration

"mutators": {
  "BCMath": {
    "settings": {
      "bcpowmod": false,
      "bcsqrt": false,
    }
  }
},

[maks-rafalko]

Thanks for creating the second awesome PR and adding support for extensions 👍

A couple of comments to discuss

[maks-rafalko]

👌

[sanmai]

Seems like this is it. Great work!

[maks-rafalko]

Thank you @majkel89 for your work and patience, really appreciate it. Great mutator!