Add infrastructure for storing a VARIADIC ANY function's VARIADIC flag.

Originally we didn't bother to mark FuncExprs with any indication whether
VARIADIC had been given in the source text, because there didn't seem to be
any need for it at runtime.  However, because we cannot fold a VARIADIC ANY
function's arguments into an array (since they're not necessarily all the
same type), we do actually need that information at runtime if VARIADIC ANY
functions are to respond unsurprisingly to use of the VARIADIC keyword.
Add the missing field, and also fix ruleutils.c so that VARIADIC ANY
function calls are dumped properly.

Extracted from a larger patch that also fixes concat() and format() (the
only two extant VARIADIC ANY functions) to behave properly when VARIADIC is
specified.  This portion seems appropriate to review and commit separately.

Pavel Stehule

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201301171
+#define CATALOG_VERSION_NO	201301211
 
 #endif

src/include/fmgr.h

@@ -624,6 +624,7 @@ extern Oid	get_fn_expr_argtype(FmgrInfo *flinfo, int argnum);
 extern Oid	get_call_expr_argtype(fmNodePtr expr, int argnum);
 extern bool get_fn_expr_arg_stable(FmgrInfo *flinfo, int argnum);
 extern bool get_call_expr_arg_stable(fmNodePtr expr, int argnum);
+extern bool get_fn_expr_variadic(FmgrInfo *flinfo);
 
 /*
  * Routines in dfmgr.c

src/include/nodes/primnodes.h

@@ -340,6 +340,7 @@ typedef struct FuncExpr
 	Oid			funcid;			/* PG_PROC OID of the function */
 	Oid			funcresulttype; /* PG_TYPE OID of result value */
 	bool		funcretset;		/* true if function returns set */
+	bool		funcvariadic;	/* true if VARIADIC was used in call */
 	CoercionForm funcformat;	/* how to display this function call */
 	Oid			funccollid;		/* OID of collation of result */
 	Oid			inputcollid;	/* OID of collation that function should use */