Clear paren level flag on \r or any backslash command, rather than

keeping parenlevel unchanged.

src/bin/psql/mainloop.c

@@ -313,6 +313,7 @@ MainLoop(PsqlSettings *pset, FILE *source)
 			{
 				const char *end_of_cmd = NULL;
 
+				paren_level = 0;
 				line[i - prevlen] = '\0';		/* overwrites backslash */
 
 				/* is there anything else on the line? */