GitLab

* Extend logging in IOFetch (and add message definitions)
* Update buffer size setting for UDP socket
* remove spaces at end of lines in other files

IOFetch is a general upstream "fetch" class that should be able to
operate over TCP or UDP.  Related changes have been made in the
associated classes.  So far, only the unit tests for a UDP fetch
have been made (and passed).

Updated function names to match convention.  Also added receiveComplete()
to prepare for the fact that a TCP receive may require multiple reads
before the complete message is read.

Admin tasks:
* Split out io_error.h from asiolink.h
* Made test files follow naming convention of main files
* More discriminatory includes in some files
* Updates tests/Makefile.am

Coding tasks:
* Add additional methods to io_socket.* and put in dummies in
  {tcp,udp}_socket.h
* Incorporated basic IO Fetch code from Scott