Detect various spacing issues in function declarations

[Eloy Lafuente]

This is about, exclusively, detect spacing issues in function/method declarations. Some cases (there may be more):

• No space between function name and open parenthesis.
• No space between close parenthesis and the return type colon.
• Space between the return type colon and the return type.
• Space before the curly brackets.
• ...

aka, correct:

function function_name(...params): ?type {