Review request for generating debian package for jdk modules

[Mandy Chung]

This change will generate debian packages for jdk modules.

Webrev at:
   http://cr.openjdk.java.net/~mchung/jigsaw/jigsaw-deb-pkgs/

Summary:
1. Include unpack200 in the jdk.boot module depended by
   the install script to uncompress the jpg generated packages.

2. Modify jpkg to handle jdk.boot module slightly differently
   than other modules - no pre-dependency and not pack200 
   compressed and also no preinst and postinst script.

3. BuildPackages.gmk is the makefile for building packages.
   Currently it checks if it's running on debian systems or not.
   If not, no package will be generated.  This gmk file will 
   be modified when jpkg is extended to support other native
   packaging format or module neutral format.

Thanks
Mandy