Failing to connect would release parts of the MYSQL struct.
We would then proceed to try again to connect without re-
initializing the struct.

We prevent the unwanted freeing of data we'll still need now.


client/mysqladmin.cc:
  Losing a connection (or not even getting on in the first place) should
  not trash the MYSQL-struct.
  
  Add a lot of comments.
  
  Rewrite re-connection fu.
sql-common/client.c:
  Assert against bad parameters usually caused by de-initing a
  MYSQL-struct without re-initing it again before re-use.