ref/lib/apilog: move logcop logging and support for contex/vtrace control.
ref/lib/apilog: move logcop logging and support for contex/vtrace control.

See v.io/i/446

Change-Id: Ic058633ebb4fd0a841872daff61090bf71fe4aa7

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref