[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.
[dcl.spec.concept] Fix examples in p7.
[dcl.spec.concept] Update wording in p8.
[various] Replace "unconstrained" with more appropriate wording.
[dcl.spec.concept] Disallow redeclaration of concepts.
[dcl.spec.concept] Update restrictions on redeclaration and
recursive concept definitions.
[edit] Update title page and regen docs.
Merge branch 'master' of https://github.com/cplusplus/concepts-ts