Revert "Revert "Use MAP_FIXED in remapNewHeap""

This reverts commit 95d2bc928952165cd84aa0c5fe5f572b7ec2c807.

Change-Id: I100b42df21048841aeae3adce67059e15e65315f
Merge "Revert "Revert "Use MAP_FIXED in remapNewHeap""" into kitkat