The size of an auxv is the machine pointer but a 64-bit integer is reserved
in a MmEntry protobuf message to store an auxv. Moreover the number of auxv's
varies from one architecture to another. So the following is proposed
to alleviate the issue.

* Introduced the type auxv_t representing a machine-pointer sized integer.

* The size of auxv array is extracted from a MmEntry message instead of using
  the value of the macro AT_VECTOR_SIZE.
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>