hg: panama/dev: Make jdk.internal.clang upgradable module

[henry.jen at oracle.com]

Changeset: e7d7e9944381
Author:    henryjen
Date:      2018-03-23 11:05 -0700
URL:       http://hg.openjdk.java.net/panama/dev/rev/e7d7e9944381

Make jdk.internal.clang upgradable module

! make/common/Modules.gmk
! test/jdk/com/sun/tools/jextract/jclang-ffi/TestJextractFFI.java
+ test/jdk/com/sun/tools/jextract/jclang-ffi/src/module-info.java