NEWS entry for resolved bug 328100 XABORT not implemented (VEX r2800).

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13753 a5019735-40e9-0310-863c-91ae7b9d1cf9
Add testcase for bug 328100 XABORT not implemented (VEX r2800).

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13754 a5019735-40e9-0310-863c-91ae7b9d1cf9