ALL: Fix typo (succesful -> successful)

Thanks to 'onlyjob' on pull request #337 for pointing out an instance of this.
BUILD: GNU Hurd & kFreeBSD support

From: Petr Salinger <Petr.Salinger@seznam.cz>
Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=711320
Bug-ScummVM: https://sourceforge.net/tracker/?func=detail&atid=418820&aid=3614268&group_id=37116
COMMON: Add depth/flat parameters to addSubDirectoryMatching.
MOHAWK: Use addSubDirectoryMatching for LB paths.
WINTERMUTE: Fix for unnecessary "WARNING: getChildren() failed for path:"

FSNode::getChildren() was called assuming that it returns 0 iff success.
Actually, it's the other way around.
WINTERMUTE: Prevent warning about duplicate files when autodetecting.

Removed a call to BaseFileManager::registerPackages() in
WintermuteEngine::getGameInfo(), as the constructor for BaseFileManager
already calls registerPackages() once; another call should thus be
superfluous.