hg: panama/dev: 8208284: Add sizeof method to Struct type

[sundararajan.athijegannathan at oracle.com]

Changeset: 9e734a3c1154
Author:    sundar
Date:      2018-07-27 09:03 +0530
URL:       http://hg.openjdk.java.net/panama/dev/rev/9e734a3c1154

8208284: Add sizeof method to Struct type
Reviewed-by: henryjen

! src/java.base/share/classes/java/foreign/memory/Struct.java
! src/java.base/share/classes/jdk/internal/foreign/ScopeImpl.java
! test/jdk/com/sun/tools/jextract/libproc/LibprocTest.java