Move some virtual memory constants to the top of the file where they are on other architectures [1].
Move some virtual memory constants to the top of the file where they are on
other architectures [1].

While here:
 - Remove an unused and commented out include.
 - Add a comment describing the file that other copies have.
 - Fix the style of the defines and add a comment on what each one is.

Suggested by:	[1] alc

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase