Set location fields, like in upstream.

I think these were left out by accident when we cherry-picked the upstream
patches to add location information to various structs.

src/backend/parser/gram.y

@@ -12086,6 +12086,7 @@ case_expr:	CASE case_arg when_clause_list case_default END_P
 					c->arg = (Expr *) $2;
 					c->args = $3;
 					c->defresult = (Expr *) $4;
+					c->location = @1;
 					$$ = (Node *)c;
 				}
 		;
@@ -12102,6 +12103,7 @@ when_clause:
 					CaseWhen *w = makeNode(CaseWhen);
 					w->expr = (Expr *) $2;
 					w->result = (Expr *) $4;
+					w->location = @1;
 					$$ = (Node *)w;
 				}
 			;

src/backend/parser/parse_expr.c

@@ -1910,6 +1910,7 @@ transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c)
 	}
 
 	newc->args = newcoercedargs;
+	newc->location = c->location;
 	return (Node *) newc;
 }
 
@@ -1948,6 +1949,7 @@ transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
 	}
 
 	newm->args = newcoercedargs;
+	newm->location = m->location;
 	return (Node *) newm;
 }