Deprecates get_userinfo() master function.

get_userinfo() function has a very ill-defined interface.
It returns an array which is usually accessed by the
*internal* symbolic constants (for indexing the
*internal* userlist structure) from userinfo.h plus an
offset. This is error-prone and the internal indices
can therefore never be changed internally.
It is also completely undocumented.

The alternative is query_userlist(). If a lot of
people need all data from the userlist at once,
an additional query function should be designed.

Change-Id: I848b764f46f609f612d1847c1e0198cd3dc454ab
diff --git a/sys/userinfo.h b/sys/userinfo.h
index c1b50af..276a72d 100644
--- a/sys/userinfo.h
+++ b/sys/userinfo.h
@@ -12,8 +12,8 @@
  * Important: these are the *internal* field indices. When obtained by
  *            get_userinfo(), the fields in the resulting array are off by +1,
  *            i.e. to get the level, you need to index with USER_LEVEL+1.
- *            TODO: change that and use either correct additional defines or a
- *            TODO::new data structure.
+ *            Therefore get_userinfo() is currently deprecated in favor
+ *            of query_userlist().
  */
 
 /* password (encrypted) */