Apply strict type checking to Complex suffix

[MarkBaker]

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Passing a true/false value to the Complex function as a suffix results in a 0 or 1 being appended to the value, and no suffix applied

So COMPLEX(1.5, 3.5, true) will result in 1.5+3.51, a totally erroneous value.