Review Request: JDK-8171418: Remove jdeps internal --include-system-modules option

[Mandy Chung]

Webrev at:
   http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8171418/webrev.00

--include-system-modules option was a temporary option added in an early stage 
of developement.  Time to remove it as a clean up.

Mandy