Use of global vars is what prevents RTL from working in Tinsel (and
probably in other engines). More specifically, the fact that many
global vars are not explicitly inited when the engine is (re)launched.
svn-id: r54262
* Fix a bug which caused coroutines invoked with nullContext to
leak their state.
Sadly, nullContext is underdocumented, yet very delicate and
full of subtleties... ./
* Move nullContext decl from sched.cpp to coroutine.cpp
* Enhance a few doxygen comments
svn-id: r53934