licenses: convert license tags to SPDX

global: isabelle update_cartouches

lib: add license header text

These two files were @TAG-ged but without copyright header text.

lib: test cases for Insulin and ShowTypes tools

Isabelle2018: new "op x" syntax; now is "(x)"

(result of "isabelle update_op -m <dir>")

globally use session-qualified imports; add Lib session

Session-qualified imports will be required for Isabelle2018 and help clarify
the structure of sessions in the build tree.

This commit mainly adds a new set of sessions for lib/, including a Lib
session that includes most theories in lib/ and a few separate sessions for
parts that have dependencies beyond CParser or are separate AFP sessions.
The group "lib" collects all lib/ sessions.

As a consequence, other theories should use lib/ theories by session name,
not by path, which in turns means spec and proof sessions should also refer
to each other by session name, not path, to avoid duplicate theory errors in
theory merges later.

Isabelle2016-1: update to new ML API

Update references to renamed ML constants; supply default arguments to
functions with additional parameters; etc.

Fix up c-parser and autocorres for AutoCorres 1.2 release.

lib: add Insulin, tool to show terms without syntax sugar.