Added support for the FLOOR.MATH and FLOOR.PRECISE functions

[paulkned]

This is:

- [ ] a bugfix
- [ x ] a new feature

Checklist:

• [ x ] Changes are covered by unit tests
• [ x ] Code style is respected
• [ x ] Commit message explains why the change is made (see /~https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• [ x ] CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

Support for FLOOR.MATH and FLOOR.PRECISE were lacking, I added them with this pull request

[PowerKiKi]

Thanks ! merged in a6c56d0