a deadlock between I/O and SQL threads in replication
when relay_log_space is too small. This fixes bug #79.


sql/log.cc:
  New variable rli->ignore_log_space_limit to resolve
  a deadlock between I/O and SQL threads in replication
  when relay_log_space is too small.
sql/slave.cc:
  New variable rli->ignore_log_space_limit to resolve
  a deadlock between I/O and SQL threads in replication
  when relay_log_space is too small.
sql/slave.h:
  New variable rli->ignore_log_space_limit to resolve
  a deadlock between I/O and SQL threads in replication
  when relay_log_space is too small.
sql/sql_repl.cc:
  New variable rli->ignore_log_space_limit to resolve
  a deadlock between I/O and SQL threads in replication
  when relay_log_space is too small.