portability fixes for systems with broken syscalls that do not interrupt on 
a signal
temporary commit - will not be pushed, need to sync up


include/my_sys.h:
  work on READ_APPEND cache
mysys/Makefile.am:
  change to test IO_CACHE
mysys/mf_iocache.c:
  work on READ_APPEND cache
BitKeeper/etc/ignore:
  Added mysys/#mf_iocache.c# mysys/test_io_cache to the ignore list
sql/mysqld.cc:
  make shutdown work on broken systems
sql/sql_repl.cc:
  make sure slave can be stopped on broken systems in all cases, clean-up