[dcl.fct] Removing unnecessary restrictions.

Also fixing some typos.
[dcl.fct] Reorder paragraphs.
[class] Updates wording.
[class.derived] Remove redundant sentence.

Missing semicolon in example.
[over.match] Update wording for viable functions and
best viable functions.
[over.over] Fix wording for overloading when taking the
address of an overloaded function.