Change block scopes to create new label scope, too.
Change block scopes to create new label scope, too.

This makes local labels work out properly. We should scan a function body
for non-local labels and add them all inside the initial function scope,
anyway, since labels can jump backward, so this shouldn't cause any
problems.

vincenthz/language-c,vincenthz/language-c,vincenthz/language-c