[DGD] mp/tls fact check

[Chris]

I began writing a help document for my lib describing some of the various things
involved in optimizing code to be compatible with the upcoming DGD MP.
I tried my best to put something sensible together, but i did not feel
much confidence
when i got to the part about TLS vars.
If there is anything i wrote incorrectly, inadequetely, or anything
important i left out, I
would love to be corrected.  Here is the document in its current state:


A thread is a single chain of code not broken up by call_outs, which originates
from either a call_out or a user sending a message.

There are three general rules which must be followed to preserve multi-threaded
compatibility.  These rules are listed here below:

 -There cannot be a private function prototype that is left undefined.

 -If a call_other to a different object would change a global variable in that
  object, and the best solution is not to use TLS vars (see below), than one
  good option is to use a 'relay function'.  A relay function is a function with
  a call_out (usually 0 seconds).  Once the function called with call_out
  executes, it does so on its own thread, and is no longer breaking this rule.

 -If more than one thread can compete to modify an external objects global
  variable, than whenever these threads are executed simultaneous one of them
  gets rescheduled.  When many threads are doing this, and rescheduling becomes
  rampant, we have created a huge drain on DGD's ability to multi-thread.  To
  avoid this we use TLS-vars.


Thanks for input,
-chris