BSTR caching

[Markus Stockhausen]

Hi,

the last week I took some time to implement the first try of BSTR
caching in oleaut.c. On the one hand this will fix a bug, on the other
hand Wine could save some CPU cycles and can catch up with the speed of
the native implementation.

Attached you will find the result of my considerations. It is not yet
ready for implementation but will reflect the "big picture" I thought
of. I would be happy to receive some feedback on this work especially
the following questions are still open:

- Is DllMain the right location for Initialization/Cleanup
- I'm totally confused about the task of how to write a testcase
  for this change.

Thanks for your help.

Markus