Finished all of the code relating to the "global server info" stuff defined

 Finished all of the code relating to the "global server info" stuff defined
in control.c.  The file "citadel.control" is the file that used to be called
"MMstructure", and "struct CitControl" used to be "struct msgmain".

 Also, the user number is now called "usernum" rather than "eternal", and
the highest existing user number is now stored in citadel.control rather than
in its own file.