mips32: mention MIPS32/Android as supported platform

Mention MIPS32/Android as supported platform in NEWS


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14498 a5019735-40e9-0310-863c-91ae7b9d1cf9
also do unshare and pivot_root on s390x


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14499 a5019735-40e9-0310-863c-91ae7b9d1cf9