hg: jdk9/sandbox/langtools: add doc for jdeprusage

[stuart.marks at oracle.com]

Changeset: 981eb84c88b2
Author:    smarks
Date:      2016-06-10 16:33 -0700
URL:       http://hg.openjdk.java.net/jdk9/sandbox/langtools/rev/981eb84c88b2

add doc for jdeprusage

! src/jdk.jdeps/share/classes/com/sun/tools/jdeprfind/JDeprFind.java
! src/jdk.jdeps/share/classes/com/sun/tools/jdeprfind/readme.md
+ src/jdk.jdeps/share/classes/com/sun/tools/jdeprusage/readme.md