Fix compilation with newer versions of GLib

GIO now contains a GMenuItem object type.

src/MainWindow.vala:300.17-300.24: error: `MenuItem' is an ambiguous reference between `GLib.MenuItem' and `Gtk.MenuItem'
MenuItem recentFileItem = (Gtk.MenuItem)builder.get_object("menubar_open_recent");
^^^^^^^^

https://bugzilla.gnome.org/show_bug.cgi?id=678003
Fix deprecation warning

src/MoUtils.vala:42.39-42.71: warning: GLib.FILE_ATTRIBUTE_STANDARD_SIZE has been deprecated since vala-0.16. Use FileAttribute.STANDARD_SIZE

https://bugzilla.gnome.org/show_bug.cgi?id=678004
make last commit work with both vala 0.12 and 0.16
Fix compile-time errors

TextIter were causing errors:
Cannot pass value to reference or output parameter

https://bugzilla.gnome.org/show_bug.cgi?id=678016
make last commit work with both vala 0.12 and 0.16
pre-release version bump
updated copyright date in about dialog
Updated Greek translation
Fix -Werror=format-security errors.
Added Polish translation
Updated Polish translation
fix bug 687230 - Segmentation fault on HexTextBuffer.vala
pre-release version bump
always append new hex output to end of textbuffer, not at cursor pos
Updated Brazilian Portuguese translation
Update Chinese simplified translation