Log Message:
p5-Coro: update to 6.52.

6.52  Tue Aug 14 18:49:43 CEST 2018
	- libcoro update: allow sharing of coro threads using the pthreads
          backend among different pthreads, as is required by Coro::Multicore.
	- always allow ->call and ->eval when the coro is the current coroutine. this
          makes it possible, among other things, to call these on $Coro::main.
	- minor code cleanups.