New function to check the permissions of GNUPGHOME and the various files

that live there for safe permission/ownership (--no-permission-warning to
disable)
The newer glibcs print scary warnings about using mktemp().  The use here
was actually safe, but the warning was bound to confuse people, so here is
an arguably better tempname creator that pulls random bits from the pool.

g10/options.h

@@ -104,6 +104,8 @@ struct {
       int keep_temp_files:1;
       STRLIST other;
     } keyserver_options;
+    int keyserver_disable;
+    int no_perm_warn;
     char *temp_dir;
     int no_encrypt_to;
     int interactive;