Fix a bug in the sign of the derivative of the transformation used with double bounded parameters.  The effect was a wrong sign applied to the gradient when transforming from external to internal parameters. This was affecting in particular the  minimizations when the analytical gradient is provided. (see http://root.cern.ch/phpBB2/viewtopic.php?t=8365 ). The effect happens only when the internal parameter was outside the [-PI/2 , PI/2] range.   The change in sign can affect also the transformation of the error matrix from internal to external. As example consider the minimization of  f(x,y) = (sin(x)-1)**2 + (x-y)**2, with x bound to [0,2]. In this case a wrong correlation was obtained when using the bound. 
Fix a bug in the sign of the derivative of the transformation used with double bounded parameters. 
The effect was a wrong sign applied to the gradient when transforming from external to internal parameters. This was affecting in particular the 
minimizations when the analytical gradient is provided. (see http://root.cern.ch/phpBB2/viewtopic.php?t=8365 ).
The effect happens only when the internal parameter was outside the [-PI/2 , PI/2] range.
 
The change in sign can affect also the transformation of the error matrix from internal to external. As example consider the minimization of 
f(x,y) = (sin(x)-1)**2 + (x-y)**2, with x bound to [0,2]. In this case a wrong correlation was obtained when using the bound. 

In the old  Minuit MNDXDI returns the module (why ??), but when calculating the transformation for the user provided gradient the correct signed 
derivative is used.


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@28280 27541ba8-7e3a-0410-8455-c3a389f83636

bbannier/ROOT,bbannier/ROOT,dawehner/root,dawehner/root,bbannier/ROOT,dawehner/root,dawehner/root,dawehner/root,bbannier/ROOT,dawehner/root,bbannier/ROOT,dawehner/root,bbannier/ROOT,dawehner/root,bbannier/ROOT