handle PIE spanning 0x55..'-0x56..' segment

[derekbruening]

The PIE range where DR is loaded is [0x5555'55555000..0x5655'55555000), with simple page alignment, meaning that DR could span the 0x55..'-0x56..' segment gap. Umbra does not support segment-spanning maps. DR has functionality already implemented to reload itself at startup to a different address, so our plan is to add a DR option requesting that DR relocate itself if the kernel placed it spanning the segments.

Xref #1782, DynamoRIO/dynamorio#1227