A terrible pile of things done to the code. Did a little bit of SM_PATH

A terrible pile of things done to the code. Did a little bit of SM_PATH
stuff in plugins.

Then I moved some files:
  src/validate.php         -> include/validate.php
  src/load_prefs.php       -> include/load_prefs.php
  src/options_personal.php -> include/options/personal.php
  src/options_display.php  -> include/options/display.php
  src/options_folder.php   -> include/options/folder.php

Basically, the concept here is that src/ should ONLY contain files that
actually get called from the web browser as a php script directly. All
of these files do not really contain functions or anything (so the
functions/ directory did not really make sense), but were more strictly
include files.

Of course, the name functions for a directory is bad organization, IMHO,
anyhow. I guess class would fall in the same category. Oh well, some of
that might get fixed someday.

So, new rule. Only put it in src/ if it gets called directly.

That was really sort of an unwritten rule before. However, since it was
never really enforced or officialized, things got sloppy.

I think I have everything fixed in the CORE with this traumatic moves. I
am sure all of the plugins will be broken. Oh well, the error messages
should be pretty loud and easy enough to fix.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@3580 7612ce4b-ef26-0410-bec9-ea0150e637f0