stylecheck: decide fate of CheckIncDec

[dominikh]

CheckIncDec flags x += 1 and recommends using x++ instead. The check exists, but isn't made available, not even as an optional check. We haven't enabled it so far because it can produce unhelpful warnings for code like the following:

x += 3
...
x += 2
...
x += 1

Either enable the check (optionally with some improvements) or remove it.

[bcmills]

Sadly, my related proposal golang/go#21263 was declined. 😉

[mwat56]

@dominikh

Either enable the check (optionally with some improvements) or remove it.

I'd say: remove it.
Using x++ (but, alas, not ++x) in Go is a bit confusing in the beginning if you've worked with ++x and --x in other languages before because it's a statement in Go instead of an expression as in other languages (not to mention the difference between ++x and x++ and what version Go actually compiles to). So you have to re-learn its use anyway in Go and probably end up with x += 1 so that recommending the use x++ wouldn't actually help.
Hence leave it to the programmer and don't interfere with a linter recommendation.