use opt_net_buffer_length instead of net_buffer_length


Makefile.am:
  netware files should always be in 'make dist'
client/mysqldump.c:
  use opt_net_buffer_length instead of net_buffer_length
configure.in:
  netware files should always be in 'make dist'
netware/Makefile.am:
  netware files should always be in 'make dist'