Replace process endpoint mutex with R/W locks
Add R/W locks to endpoints
Update ipc_send() to use revamped locks
Update ipc_receive() to use revamped locks
Update ipc_sendEndpoint() to use revamped locks
Update ipc_receiveEndpoint() to use revamped locks
ipc_sendEndpoint(): unlock transmitted endpoint's lock
Update ipc_createNullbound() to use revamped locks
Update ipc_createSelfbound() to use revamped locks
Merge branch 'master' into revamp-ipc-locking
ipc_sendEndpoint(): typos