Fix 341789 - aarch64: shmat fails with valgrind on ARMv8
arm64, like amd64, must not use VKI_IPC_64, even
if this symbol is defined.
This makes the shmctl fail, which results in a zero size returned,
which means that the succesful shmat is not reported to the aspacemgr.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14821 a5019735-40e9-0310-863c-91ae7b9d1cf9