Fix configure for Free BSD

* seems that /usr/local is not in the default ld path on FreeBSD, so add
  it manually

* search for wget_wch instead of get_wch, on FreeBSD get_wch seems to be
  available as a macro, which does not automatically mean that wide char
  support is really available
Merge pull request #11 from jin-eld/freebsd

Fix configure for Free BSD