for July 17: early crash on x86-64)

SELinux needs MAY_APPEND to be passed down to the security hook.
Otherwise, we get permission denials when only append permission is
granted by policy even if the opening process specified O_APPEND.
Shows up as a regression in the ltp selinux testsuite, fixed by
this patch.
Signed-off-by: NStephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>