Predict integer overflow to avoid buffer overruns.

Several functions, mostly type input functions, calculated an allocation
size such that the calculation wrapped to a small positive value when
arguments implied a sufficiently-large requirement.  Writes past the end
of the inadvertent small allocation followed shortly thereafter.
Coverity identified the path_in() vulnerability; code inspection led to
the rest.  In passing, add check_stack_depth() to prevent stack overflow
in related functions.

Back-patch to 8.4 (all supported versions).  The non-comment hstore
changes touch code that did not exist in 8.4, so that part stops at 9.0.

Noah Misch and Heikki Linnakangas, reviewed by Tom Lane.

Security: CVE-2014-0064
pushStop(TSQueryParserState state)
{
	QueryOperand *tmp;

	tmp = (QueryOperand *) palloc0(sizeof(QueryOperand));
	tmp->type = QI_VALSTOP;

	state->polstr = lcons(tmp, state->polstr);
}

pushStop(TSQueryParserState state)
{
	QueryOperand *tmp;

	tmp = (QueryOperand *) palloc0(sizeof(QueryOperand));
	tmp->type = QI_VALSTOP;

	state->polstr = lcons(tmp, state->polstr);
}
