patch 9.0.1007: there is no way to get a list of swap file names

Problem:    There is no way to get a list of swap file names.
Solution:   Add the swapfilelist() function.  Use it in the test script to
            clean up.  Remove deleting individual swap files.
diff --git a/src/proto/memline.pro b/src/proto/memline.pro
index 364f0aa..3fa8707 100644
--- a/src/proto/memline.pro
+++ b/src/proto/memline.pro
@@ -10,7 +10,7 @@
 void ml_close_notmod(void);
 void ml_timestamp(buf_T *buf);
 void ml_recover(int checkext);
-int recover_names(char_u *fname, int list, int nr, char_u **fname_out);
+int recover_names(char_u *fname, int do_list, list_T *ret_list, int nr, char_u **fname_out);
 char_u *make_percent_swname(char_u *dir, char_u *name);
 void get_b0_dict(char_u *fname, dict_T *d);
 void ml_sync_all(int check_file, int check_char);