[Clp] restricted basis entry rule

[John Forrest]

Osman,

I have added functionality to trunk/Clp.  Look for CLP_USER_DRIVEN1 in
ClpSimplexPrimal.cpp.  Dummy versions of the functions are in
Clpmain.cpp so Clp will compile with CXXDEFS="-DCLP_USER_DRIVEN1".

Code changes along these lines may be of interest to other advanced
users of Clp.  Some of this functionality is in Osi with
enableSimplexInterface etc, but that deliberately implements actions in
a slow way and without certain things that may be essential for
robustness e.g. scaling.  This approach aims to put hooks deep down
inside Clp (at present just for primal).

If there are other similar requests, I can add more such hooks.

The code compiles and runs when functions are dummy ones.  I am unable
to tell whether there is sufficient functionality for what you need to
do, but it is a first step.

John Forrest