x86 - hide X86_VM_MASK from userland programs v3

X86_VM_MASK is kernel specific flags so hide it from userland programs.

It should be defined *before* ptrace.h inclusion because of circular
link between these files

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>