9696 add /etc/system.d support
Portions contributed by: Andy Fiddaman <andy@omniosce.org>
Reviewed by: Hans Rosenfeld <hans.rosenfeld@joyent.com>
Reviewed by: Peter Tribble <peter.tribble@gmail.com>
Reviewed by: C Fraire <cfraire@me.com>
Reviewed by: Toomas Soome <tsoome@me.com>

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- *ident  "%Z%%M% %I%     %E% SMI" /* SVR4 1.5 */
  *
  * CDDL HEADER START
  *
  * The contents of this file are subject to the terms of the
  * Common Development and Distribution License, Version 1.0 only
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  *
  *
  * SYSTEM SPECIFICATION FILE
  *
  
+ * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! NOTE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+ *
+ * It is not recommended to edit this file directly but rather
+ * to deliver configuration fragments into files under /etc/system.d;
+ * files in /etc/system.d are combined in alphabetical order and read by
+ * the kernel before this file (/etc/system) is processed.
+ *
+ * Refer to the system(4) manual page for more information and
+ * recommendations on naming fragment files.
+ *
+ * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! NOTE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+ 
  * moddir:
  *
  *       Set the search path for modules.  This has a format similar to the
  *       csh path variable. If the module isn't found in the first directory
  *       it tries the second and so on. The default is /kernel /usr/kernel