Make the new task synchronize the particles hit by feedback and force them to recompute a time-step. Propagate the time-step upwards.

Version that correctly flags the BHs to swallow and removes them before dying in the time-step calculation function.

Split the star formation task into two parts: The star formation bit and the resorting bit. Move the sf_count communication to just depend on the first one in order to speed things up.

Revert "Activate star tasks also if we are running with SF on and the cell is active for hydro purposes."

This reverts commit 8a1c735c.

Added communication functions to propagate the new number of star particles after a SF event has occured.

replace the cell's mpi.stars.recv and recv_ti task pointers with the new linked recv pointers. goodbye, mpi.stars!

replace the cell's mpi.grav.recv and recv_ti task pointers with the new linked recv pointers. added some utility functions for looking up send/recv tasks of a given subtype in a cell.

replace the cell's mpi.hydro.recv_ti task pointer with the new linked recv pointers. goodbye, mpi.hydro!

merge all send tasks of all types into a single linked list. this is easier than doing the recv tasks since they are already linked lists to begin with.

collapse the hydro send tasks into one single linked list, modify scheduler_activate_send to look for a specific task subtype.