hg: panama/dev: Add support for UnexposedDecl

[henry.jen at oracle.com]

Changeset: a2f7bf54a901
Author:    henryjen
Date:      2018-05-23 12:35 -0700
URL:       http://hg.openjdk.java.net/panama/dev/rev/a2f7bf54a901

Add support for UnexposedDecl

! src/jdk.jextract/share/classes/com/sun/tools/jextract/Context.java
! src/jdk.jextract/share/classes/com/sun/tools/jextract/HeaderFile.java
! test/jdk/com/sun/tools/jextract/JextractToolProviderTest.java