• Fixed #97
• Fixed gtk_box_gadget_distribute: assertion 'size >= 0' failed in GtkSpinButton errors in synthicc.xrc.
• Removed libgtkd-3-dev dependency, which should be a typo and not necessary for DisplayCAL.
• Fixed gtk_box_gadget_distribute: assertion 'size >= 0' failed in GtkSpinButton errors in 3dlut.xrc.
• Replaced all string concatenations with format commands on possible code paths to fix the #86.
• Manually applied changes of #99 of @gavtroy.