Fix is to remove any references to the current hostname when running
mysql_install_db --cross-bootstrap.  (The dist-hook make target makes
this call, and the resulting data directory is included in the source
distribution as win/data/*.)

Also, a few other clean-ups to mysql_install_db while there.


Makefile.am:
  Adapt to clean-up in mysql_install_db (--windows becomes --cross-bootstrap)
scripts/mysql_install_db.sh:
  Filter out references to the current hostname when performing
  a cross-bootstrap installation by removing any lines which
  contain the string "@current_hostname".
  
  Deprecate the old --windows option; use --cross-bootstrap
  instead, since it more accurately reflects the purpose.
  
  Other clean-up: the wrong syntax was being used to test the
  exit status of mysqld --bootstrap.  It mostly worked, as long
  as mysqld succeeded.  However, it was not robust.
scripts/mysql_system_tables_data.sql:
  Rename local @hostname variable to @current_hostname, which is a more
  unique label to search on.  mysql_install_db now filters out all
  lines which include "@current_hostname" during a --cross-bootstrap
  installation.