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

src/backend/utils/adt/tsquery_util.c

@@ -334,6 +334,11 @@ QTN2QT(QTNode *in)
 	QTN2QTState state;
 
 	cntsize(in, &sumlen, &nnode);
+
+	if (TSQUERY_TOO_BIG(nnode, sumlen))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("tsquery is too large")));
 	len = COMPUTESIZE(nnode, sumlen);
 
 	out = (TSQuery) palloc0(len);