Added weak callbacks, hid THROW_ERROR macro.
Added weak callbacks, hid THROW_ERROR macro.

Conflicts:
	nan.h

eljefedelrodeodeljefe/nan,gagern/nan,noahjs/nan,lovell/nan,durai145/nan,nodejs/nan,thefourtheye/nan,evanlucas/nan,saper/nan,noahjs/nan,durai145/nan,fleg/nan,nodejs/nan,eljefedelrodeodeljefe/nan,evanlucas/nan,nodejs/nan,fleg/nan,ipmobiletech/nan,gastrodia/nan,eljefedelrodeodeljefe/nan,saper/nan,saper/nan,mikolalysenko/nan,gagern/nan,addaleax/nan,lovell/nan,eljefedelrodeodeljefe/nan,thefourtheye/nan,mscdex/nan,thefourtheye/nan,thejinx0r/nan,LinusU/nan,thejinx0r/nan,ipmobiletech/nan,sesh-kebab/nan,hmalphettes/nan,mscdex/nan,mikolalysenko/nan,noahjs/nan,addaleax/nan,ipmobiletech/nan,hmalphettes/nan,sanemat/nan,sesh-kebab/nan,LinusU/nan,noahjs/nan,durai145/nan,thejinx0r/nan,mikolalysenko/nan,saper/nan,fleg/nan,addaleax/nan,hmalphettes/nan,lovell/nan,gastrodia/nan,gastrodia/nan,guymguym/nan,mikolalysenko/nan,guymguym/nan,guymguym/nan,LinusU/nan,mscdex/nan,thejinx0r/nan,mscdex/nan,addaleax/nan,gastrodia/nan,sanemat/nan,fleg/nan,guymguym/nan,sanemat/nan,sesh-kebab/nan,sesh-kebab/nan,evanlucas/nan,Jonekee/nan,lovell/nan,thefourtheye/nan,durai145/nan,hmalphettes/nan,ipmobiletech/nan,Jonekee/nan,sanemat/nan,gagern/nan,evanlucas/nan,Jonekee/nan,Jonekee/nan,nodejs/nan,LinusU/nan