mvn.bat incorrectly detects OS on Windows NT or XP with Novell login

On Windows NT or XP with Novell Client Login mvn.bat incorrectly selects OS as Win9x, because Novell sets OS environment variable to WINNT instead of Windows_NT.
As a result it processes command line arguments as in windows 9x, what is very inconvenient because all arguments with = (equals) sign must be quoted on command line. For example -DdownloadSources=true must be quoted as "-DdownloadSources=true".

The reason for such behaviour is that mvn.bat checks in several places if "%OS%"=="Windows_NT" and this statement yields false on windows with novell login. On winnt with novell login OS is set to WINNT instead of Windows_NT.

I attached corrected mvn.bat and mvnDebug.bat that check additionally for "%OS%"=="WINNT".