flow: handled declared labels better

flow: handled declared labels better

You sometimes have code like:

{
	__label__ __out;

	blah(); blah(); blah();

__out:
	x;
}

Smatch was merging all the goto states together so you would get weird
states suddenly after calling a macro because it would pull in goto states
from earlier when the macro was called the first time.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>