Changed maps output in debuggerd.

Now the map output is only sent to the tombstone, and the entire
contents of /prod/$PID/maps is logged, not just 3 lines.  Additionally,
crasher now supports "crasher SIGSEGV-non-null", which attempts to write to a
dereferenced function address, causing a SIGSEGV at a non-zero address.
This new crasher mode can be used to test the new maps output.

Bug: 15343662
Change-Id: I796d92e8352a6b9714bbbfe96f3143c56565ef2f