Declare a couple of variables inside not outside a PG_TRY block.

I went through the buildfarm's reports of "warning: variable 'foo'
might be clobbered by 'longjmp' or 'vfork' [-Wclobbered]".  As usual,
none of them are live problems according to my understanding of the
effects of setjmp/longjmp, to wit that local variables might revert
to their values as of PG_TRY entry, due to being kept in registers.
But I did happen to notice that XmlTableGetValue's "cstr" variable
doesn't need to be declared outside the PG_TRY block at all (thus
giving further proof that the -Wclobbered warning has little
connection to real problems).  We might as well move it inside,
and "cur" too, in hopes of eliminating one of the bogus warnings.

src/backend/utils/adt/xml.c

@@ -4926,10 +4926,8 @@ XmlTableGetValue(TableFuncScanState *state, int colnum,
 				 Oid typid, int32 typmod, bool *isnull)
 {
 #ifdef USE_LIBXML
-	XmlTableBuilderData *xtCxt;
 	Datum		result = (Datum) 0;
-	xmlNodePtr	cur;
-	char	   *cstr = NULL;
+	XmlTableBuilderData *xtCxt;
 	volatile xmlXPathObjectPtr xpathobj = NULL;
 
 	xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableGetValue");
@@ -4943,13 +4941,15 @@ XmlTableGetValue(TableFuncScanState *state, int colnum,
 
 	*isnull = false;
 
-	cur = xtCxt->xpathobj->nodesetval->nodeTab[xtCxt->row_count - 1];
-
 	Assert(xtCxt->xpathscomp[colnum] != NULL);
 
 	PG_TRY();
 	{
+		xmlNodePtr	cur;
+		char	   *cstr = NULL;
+
 		/* Set current node as entry point for XPath evaluation */
+		cur = xtCxt->xpathobj->nodesetval->nodeTab[xtCxt->row_count - 1];
 		xtCxt->xpathcxt->node = cur;
 
 		/* Evaluate column path */