COMP: vtkMRMLColorLogic: Fix windows build error related to isspace

Since the function "std::isspace" is declared in <local>, but <local>
library is not found in VS2008 STL, this commit includes "ctype.h" where
isspace() function is declared.

This commit fixes the following error:

42>45>..........\Slicer-1\Libs\MRML\Logic\vtkMRMLColorLogic.cxx(1453) : error C2039: 'isspace' : is not a member of 'std'

From: Andras Lasso <lasso@queensu.ca>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24750 3bd1e089-480b-0410-8dfb-8563597acbee