make a copy of the configuration string

- when using a string to configure zlog, then make a copy of the
  original string as strsep destroys it.
add support for zlog reload with a configuration as string

- add new API (zlog_reload_from_string) that will reload the zlog
  configuration from a string parameter.
replace strsep with a custom code

- replace strsep with a custom version of fgets which
  splits a big string into independent lines.
initial zlog support for windows

- disable features like pipes or syslog.
- use custom functions for various apis that didn't work
  properly or didn't exist on Windows (gethostname, fsync,
  etc) and keep them in a separate file zlog_win.c.
- disable various unix specific calls which we can afford
  to not use for now.
Merge branch 'elis_dev'