Reject continue/break statements within members of local functions nested within

loop and switch statements, by teaching Scope that a function scope never has
a continue/break parent for the purposes of control flow. Remove the hack in
block and lambda expressions which worked around this by pretending that such
expressions were continue/break scopes.

Remove Scope::ControlParent, since it's unused.

In passing, teach default statements to recover properly from a missing ';', and
add a fixit for same to both default and case labels (the latter already
recovered correctly).

llvm-svn: 150776