Fix signal exports
Fix ccall in GtkLinkButton
Fix constructor and ccall in GtkVolumeButton
Fix deprecations in GtkSpinButton
Add missing label to GtkAspectFrame
Much more extensive testing
Use bytestring() in GtkAspectFrame ccall
Merge branch 'tests' of github.com:timholy/Gtk.jl into timholy-tests

Conflicts:
	src/Gtk.jl
fix #17