Warning for shadowing format needs to be more like warning for emacs

[briangmilnes]

• Warning 274:

• Implicitly opening namespace 'test.fstar.final.' shadows module 'testmain'
  in file "/home/milnes/Tuff/FinalFlog/test/src/fstar/fst/TestMain.fst".
• Rename
  "/home/milnes/Tuff/FinalFlog/test/src/fstar/fst/TestMain.fst"
  to avoid conflicts.

is not like Warning N: at
and the emacs regexps that match compilation errors don't like multiple lines.
I've tried and can't get this to match.

It's simplest just to make the error file single line in the system.
I have the warnings/errors matching and a very nice way to configure fstar-mode for
working with Forge and opam vs local (everest) install vs a system compile (with all
the right includes working). I'll doc it on the wiki soon.

[briangmilnes]

And it's printing the wrong case too:

• Implicitly opening namespace 'test.fstar.final.' shadows module 'testmain'