If a thread is killed in the server, we throw "shutdown" only if one is actually in
progress; otherwise, we throw "query interrupted".

Control-C in the mysql command-line client is "incremental" now.
First Control-C sends KILL QUERY (when connected to 5.0+ server, otherwise, see next)
Next  Control-C sends KILL CONNECTION
Next  Control-C aborts client.

As the first two steps only pertain to an existing query,
Control-C will abort the client right away if no query is running.

client will give more detailed/consistent feedback on Control-C now.


client/mysql.cc:
  Extends Control-C handling; enhances up feedback to user.
  
  On 5.0+ servers, we try to be nice and send KILL QUERY first
  if Control-C is pressed in the command-line client, but if
  that doesn't work, we now give the user the opportunity to
  send KILL CONNECTION with another Control-C (and to kill the
  client with another Control-C if that somehow doesn't work
  either).
mysql-test/t/flush_read_lock_kill.test:
  we're getting correct "thread killed" rather than
  "in shutdown" error now
mysql-test/t/kill.test:
  we're getting correct "thread killed" rather than
  "in shutdown" error now
mysql-test/t/rpl000001.test:
  we're getting correct "thread killed" rather than
  "in shutdown" error now
mysql-test/t/rpl_error_ignored_table.test:
  we're getting correct "thread killed" rather than
  "in shutdown" error now
sql/records.cc:
  make error messages on KILL uniform for rr_*()
  by folding that handling into rr_handle_error()
sql/sql_class.h:
  Only throw "shutdown" when we have one flagged as being in progress;
  otherwise, throw "query interrupted" as it's likely to be "KILL CONNECTION"
  or related.