Decidable.Equality: Add DecEq (Vect n a) instance
Remove unneeded lemma
Decidable.Equality: "Inline" vectDecEq
Improves upon/fixes idris-lang/Idris-dev#530
Fixes idris-lang/Idris-dev#512
Remember whether implicits are machine generated

This way, we can skip a huge chunk of coverage checking if we know the
case was generated by the machine rather than a programmer.
Fixes #535
Remove forcing optimisation from coverage checker

Because it turns out to be unsound! But using implicit arguments has the
same effect and is (I think...) sound.
Fix parsers dependency to == 0.9

Because otherwise, the parser inexplicably stops working.
Merge branch 'vect-deceq' of https://github.com/reynir/Idris-dev into reynir-vect-deceq
Merge branch 'feature/simplifiedparsing' of https://github.com/ahmadsalim/Idris-dev into ahmadsalim-feature/simplifiedparsing
Merge branch 'feature/nocolourrepl' of https://github.com/ahmadsalim/Idris-dev into ahmadsalim-feature/nocolourrepl