[RFC] [MSVCRT] Removing the MSVCRT() hack

[Dimitrie O. Paun]

Here is a patch that separates the implementation headers
from the public ones. It's not yet ready for inclusion,
but it's pretty close, so I'm sending it off to the list
for comments.

Some of the things in here:
  -- cleanup of naming conventions. Things shared with the
     public header *always* start with MSVCRT_
  -- stuff that's private, doesn't start with MSVCRT_
     From this two rules follows that a symbol starts
     with MSVCRT_ if and only if it's shared with the
     public headers, where it appears without MSVCRT_
  -- most private functions start with msvcrt_ now,
     a convetion that was already in place, but not
     followed to the letter
  -- there is a sh script that uses this simple rule
     to generate the test file. Do we integrate the
     script with the build system?

What's left to do:
  -- if we keep the test generation script, it needs to
     get integrated in the build system
  -- there are still a bunch of functions that are shared
     with the public headers that don't have the MSVCRT_
     prefix. They need to be renamed
  -- more cleanup in the public headers, remove the
     MSVCRT_ from the sentries.

Comments, flames, etc. appreciated. It's been sitting on my
HD long enough, it's time to get it into the tree.