Fixes not accepting colon spam with goto labels, adds support for paren-less sleep calls

[Altoids1]

Fixes #518.

Summary

In this PR is also a little new tool for the codebase: A defer pattern I found for C#. Here, it is used to consume whitespace regardless of which control flow in ProcStatementFromExpression does the returning. I figure it will be useful in many other places in the codebase later on.

Changelog

• Goto labels with an exaggerated amount of colons, ::::LIKE_THIS::::, are now parsed correctly.
• Calling sleep without any parentheses (as in sleep 40) is now properly implemented.
• Attempting to make a label called sleep now compiletimes, as per parity.