Fix compilation on mingw32 (windows)

Reported on the mailing list. Compilation error was:
In member function 'void vtkGDCMThreadedImageReader::ReadFiles(unsigned int, const char**)':
error: 'SYSTEM_INFO' was not declared in this scope   SYSTEM_INFO info;   ^
Prevent warning when NOMINMAX is already defined
Add more test for new vtkGDCMImageReader2 class
add check to detect out of bound access
Fix a serious issue when loading a series of 2D DICOM files
Add a simple example to check computation of spacing is ok
import commit e638a068bd6a1a6f6188910897153b3385e5af4f
Remove non-ASCII characters

Remove also gdcm:: prefix when not needed
Remove non-ASCII char