Rewrite reflow

An alternative implementation of "Reflow paragraph" command

This one does not use SCI_LINESSPLIT command from Scintilla. Instead, it's reimplemented in a way similar to how the "Line breaking" option works. The behaviour of "Line breaking" and "Reflow paragraph" should now be consistent.

Hopefully, this change fixes a couple of bug reports:

  1. https://sourceforge.net/tracker/index.php?func=detail&aid=3293009&group_id=153444&atid=787791
  2. https://sourceforge.net/tracker/index.php?func=detail&aid=2982136&group_id=153444&atid=787791
  3. http://sourceforge.net/tracker/index.php?func=detail&aid=2871809&group_id=153444&atid=787791
  4. http://sourceforge.net/tracker/index.php?func=detail&aid=2923338&group_id=153444&atid=787791

I described everything more precisely in a recent post to Geany mailing list:
http://lists.uvena.de/geany/2012-March/007960.html