Partial revert "Remove ioprio_get(2) and ioprio_set(2) from LP64."

Put them back for ARM32. Some pre-L blobs link with it
This partially reverts commit 607341e226912d95d03216483bdcef6f8d96f8b4.

Change-Id: If8503bd5624869ba071fdd21fa48cffb65617586
bionic: Add flag to restore legacy mmap behavior

* Pre-lollipop mmap would not care whether offset was signed
  or unsigned.
* Lollipop adds 64-bit support which results in sign extension
  of offset, causing a negative offset when
  a positive offset > 2^31 is given.

Change-Id: I5d19d898fc131cf848217974915d1b466a474f99