ntlv/ghe-objc-mode

Replace ghe +/- for additions and removals and use ÷/× instead which is harder to confuse with obj-C +/- for class/instance method.

ghe-objc-mode

Replace ghe +/- for additions and removals and use ÷/× instead which is harder to confuse with obj-C +/- for class/instance method.

Derived from the excellent https://github.com/DaveRandom/cloud-to-butt-mozilla