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/include/tsearch/ts_type.h

@@ -13,6 +13,7 @@
 #define _PG_TSTYPE_H_
 
 #include "fmgr.h"
+#include "utils/memutils.h"
 #include "utils/pg_crc.h"
 
 
@@ -244,6 +245,8 @@ typedef TSQueryData *TSQuery;
  * QueryItems, and lenofoperand is the total length of all operands
  */
 #define COMPUTESIZE(size, lenofoperand) ( HDRSIZETQ + (size) * sizeof(QueryItem) + (lenofoperand) )
+#define TSQUERY_TOO_BIG(size, lenofoperand) \
+	((size) > (MaxAllocSize - HDRSIZETQ - (lenofoperand)) / sizeof(QueryItem))
 
 /* Returns a pointer to the first QueryItem in a TSQuery */
 #define GETQUERY(x)  ((QueryItem*)( (char*)(x)+HDRSIZETQ ))