Fix use of Hunspell on Linux

- Method names on Linux are uppercase; Windows uses different
  methods starting with lowercase character
- Initialize and Uninitialize methods are called differently on
  Linux
- Removed left-over copying of Enchant files from BuildInclude file
- Update dependencies: now require libhunspell-dev

Change-Id: I3022d3dc57b1f06262977ba8ea69d7dc606ee67c