Prepare the measurement facility which is currently only used by oprofile
for multiple users.  To achieve that the measurement alert interrupt control
bit needs to be protected.  The measurement alert definitions are moved
to a header file and an interrupt mask is added so that users can discard
interrupts if they are for a different measurement subsystem.

Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>