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.
The C-parser contains a full parser for __asm__ syntax but
up until now hasn't done anything with it. Instead we export
some semantics. It's unspecified exactly what these semantics
are but they are parametrised with the __asm__ semantics that
went in to them, so the translation validation has something
to reason about.
Tweak modifies proofs as a result, and add some more test files.
The global-object pointer validity assertion is now created at
export time, and the graph refine mechanism now proves them. It
seems they were forgotten about once again in adjusting the globals
logic.