change the way the master lock is handled in libev stubs
change the way the master lock is handled in libev stubs

Ignore-this: c6183dc897324d1a6065bf163d20e02b

Instead of checking in each libev callback whether the runtime system
must be re-acquired, we tell libev not to invoke pending callbacks and
we execute them ourself outside the blocking section.

darcs-hash:20120614083110-c41ad-9c5f76a7874ecc855bceec4355a40b4303383314.gz

avsm/lwt-OLD,avsm/lwt-OLD