[PATCH] comm write and commfd_table cleanup

This patch performs SourceLayout shuffling and polish on some bits of
the comm layer.

  * the old commfd_table moved to Comm::Io::iocb_table
  this table is private internal to the comm layer and stores the
pending read/write IO AsyncCall and buffers while waiting on the lower
level FD loops.

  * moves comm_io_callback_t to a class Comm::Io::Callback.

  * moves the commio_* functions to methods of the Callback class.

The existing accessor macros COMMIO_FD_READCB(fd) /
COMMIO_FD_WRITECB(fd) produce a Callback* for use within the comm layer
to access entries in the table and the methods manipulating them.

  * de-duplicates the comm_write functions into two global functions
overloaded called Comm::Io::Write(...).

  * updates all the callers using comm_write() legacy wrappers to now
create their own appropriate AsyncCall callback.

* drops the "-listener" bit from libcomm* making comm/libcomm.la

Purely code shuffling. No operational changes are expected from this.

Amos

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