when passed to Printf, %l%n%L should be interepreted as %u, not %d
a testsuite to measure format behavior changes and the effectiveness of legacy mode
Add support for ignored scan_get_counter formats (%_[nlNL])
temporary bootstrap (%_[nlNL] not yet in the typer)
add typer support for the new formats
finish %_[nlNL] bootstrap
testsuite for %_[nNlL]
[minor] introduce type aliases for simple padding and precision types
toplevel: add error-reporting to environment initialization

The usual problem with catching error to report them is that it
destroys the usefulness of the backtrace information, that is
sometimes more helpful to understand the nature of the
problem. I think that only catching `Env.Error` exceptions is a good
compromise: failures that are really caused by typing environment
initialization will be reported in a clear way, and unknown failure
conditions (eg. actual bugs in the compiler) still give us a useful
backtrace.
Revert "Avoid format strings to generate .annot files; just switching to basic Format function gives a 25% speedup over total compilation time for 'ocamlc.opt -annot' applied to typing/typecore.ml."

This reverts commit 52e9f4fe9fac8b2c097e16ae305225e83dc4f954.
use Printf instead of Format in stypes.ml
typecore.ml: fix format's expected-type mistake