move register, unregister and watching direction change into event_ops

Signed-off-by: Alejandro Mery <amery@geeks.cl>
libev: get rid of lws_libev_init_fd_table() by using event_ops->init()

Signed-off-by: Alejandro Mery <amery@geeks.cl>
Move lws_plat_init_fd_tables into event_ops

Signed-off-by: Alejandro Mery <amery@geeks.cl>
Revert "Move lws_plat_init_fd_tables into event_ops"

This reverts commit 2d714dc5bf1e36dbd9419ed6491c90b9d7a43be0.