Let __bt_put() accept the R_SETCURSOR flag, as stated in the dbopen(3) manpage.

While here, update the comment above with all the accepted flags.

Reviewed by:	silence on hackers@
MFC after:	2 weeks

lib/libc/db/btree/bt_put.c

@@ -55,7 +55,7 @@ static EPG *bt_fast(BTREE *, const DBT *, const DBT *, int *);
  *	dbp:	pointer to access method
  *	key:	key
  *	data:	data
- *	flag:	R_NOOVERWRITE
+ *	flag:	R_NOOVERWRITE, R_SETCURSOR, R_CURSOR
  *
  * Returns:
  *	RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key is already in the
@@ -91,6 +91,7 @@ __bt_put(const DB *dbp, DBT *key, const DBT *data, u_int flags)
 	switch (flags) {
 	case 0:
 	case R_NOOVERWRITE:
+	case R_SETCURSOR:
 		break;
 	case R_CURSOR:
 		/*