Set GettextTools bundle version from gettext's version info.

Never to be out of date again.
Set Poedit.app's CFBundleVersion from git.
Make admin/chversion.sh update Poedit.app version as well.
Fix bogus non-fatal errors in one of Xcode scripts.
Don't set wxAboutBox version info on OS X, let it use Info.plist.
Increase version to 1.6beta1.
Add option to check beta versions appcast feed.
Move appcasts to releases.poedit.net.
Fix crash introduced when fixing int/size_t warnings.
Xcode: Build wxWidgets using the latest SDK too.
Fixes to pt_BR translation.