trustee: share trustee header path formatting

Move the shared GRANT/REMOVE/REVOKE header path formatting into trustee.c.

The Novell trustee tools display the server and volume separator as
SERVER/SYS: while keeping the remaining path separators as DOS backslashes.
Use one trustee_header_path() helper for that formatting instead of keeping
separate local copies in GRANT, REMOVE and REVOKE.

No behavior change.

trustee.h

@@ -45,6 +45,7 @@
 
 int trustee_parse_right_word(char *s, uint16 *rights);
 void trustee_rights_bracket(uint16 rights, char *out);
+void trustee_header_path(char *out, char *path, int max);
 uint32 trustee_lookup_object(char *name, uint16 *objtype, int objtype_given);
 int trustee_path_is_dir(char *path);