Disable COMMAND.COM debugging messages for 0.4 release

During my work on CORE-9773 I introduced some debugging messages in COMMAND.COM that should appear in order if everything runs correctly (a welcome message was also added). I currently still need them in order to control that the "DOS VDM reentry" feature works as expected & is foolproof; however those messages are printed in any case when a new COMMAND.COM is started (i.e. when one starts manually COMMAND.COM or when the NTVDM-embedded COMMAND.COM is started, i.e. whenever ntvdm starts and when a 32-bit app starts a 16-bit app).
If this doesn't actually constitute a problem, it may however mess up the display if a 16-bit console app starts in background a COMMAND.COM where it doesn't expect any screen output to be done. Related to that, somebody reported this inconvenience in the forums: http://www.reactos.org/forum/viewtopic.php?f=25&t=14620
Therefore I suggest that for the 0.4 release we disable those messages. In commit 70365 I introduced the needed compile-time feature to do so: a commented #define NDEBUG and the debugging messages enclosed in suitable #ifndef blocks. In trunk the #define is disabled, since I need those messages. In the 0.4 release branch, after suitable synchronization, this #define should however be enabled by hand in order to remove the messages, see line 20 in http://svn.reactos.org/svn/reactos/trunk/reactos/subsystems/mvdm/dos/command.S?annotate=70365&pathrev=70365#l20 .