The current shared_ptr implementation is efficient, but does not support
polymorphic types.
Rename it in order to make room for a polymorphic shared_ptr.
This function belongs to a group of functions for associating futures
with time points. Currently there's only now(), which servers as a shorthand
for make_ready_future<>().
Recursion takes up space on stack which takes up space in caches which
means less room for useful data.
In addition to that, a limit on iteration count can be larger than the
limit on recursion, because we're not limited by stack size here.
Also, recursion makes flame-graphs really hard to analyze because
keep_doing() frames appear at different levels of nesting in the
profile leading to many short "towers" instead of one big tower.
This change reuses the same counter for limiting iterations as is used
to limit the number of tasks executed by the reactor before polling.
There was a run-time parameter added for controlling task quota.
when_all(f1, f2) returns a future that becomes ready when all input futures
are ready. The return value is a tuple with all input futures, so the values
and exceptions can be accessed.
