1.5.2

Unified adding remote sources as input to a beacon. The add/remove functions of a beacon
are now named beacon_add_ and beacon_remove_. All platforms can add/remove
a remote beacon source. Windows and Posix targets can add/remove file descriptors. Windows
can also add/remove a OS handle.

Changed pipe to always provide a file descriptor, and renamed function to
pipe_read_fd/pipe_write_fd to match new beacon function naming. Windows platform still
has pipe_read_handle/pipe_write_handle to access the OS handles.

Fix an uninitialized variable in event streams causing beacon to not be fired before first
process to event_steam_process on the event stream.

Change path_clean to always uppercase Windows drive letters.

Add stderr to process standard streams interface.

Fix time_system on Apple platforms to return time since Epoch like other platforms.