Remove static/instance flag in check-method

Problem

The function clojure.core.typed.check.method/check-function takes an extra
argument that can be easily inferred from other arguments.

Solution

Delete the inst? flag and decide whether we have a static/instance method based
on the expression argument.

Pull request: 40
Patch: ctyp-253.patch
Commit: 9a217f
Release: 0.3.9