Add a flag to build utop-camlp4 conditionally.
Replace pa_optcomp with cppo.
Get rid of lwt.syntax.
Update deprecated License value in _oasis.
Remove compatibility with pre-4.01.0.
Remove unused/deprecated autodetection from myocamlbuild.ml.

FINDLIB_VERSION is not used anymore.

compiler-libs are provided as a package in findlib >=1.4.

errors.cmi is now provided by compiler-libs.
Migrate from deprecated Format functions.
Fix myocamlbuild expunge code that broke after 0.3->0.4 OASIS migration.
Make --disable-camlp4 the default.
Print out a nice message if trying to load camlp4 with no support.

This handles #camlp4o;; #camlp4r;; and also indirect cases
like #require "sexplib.syntax";;.
Merge pull request #103 from diml/die-camlp4-die

Remove hard dependency on camlp4