Use libunwindbacktrace for debug malloc code.

Use libunwindbacktrace for debug malloc code.

Create a method of disabling the debug allocation code paths so that
it's possible to use the libunwindbacktrace library without any
modifications.

Use this path to create and destroy the maps for the process. It's not
stricly necessary in the init code since the symbols are not modified
until after the initialize calls.

Also, remove the debug_XXX source files that doesn't need to be in libc.so.

Fix the maps reading code since it was completely broken for 64 bit.

Bug: 16408686

(cherry picked from commit 861c0ef37bcfcae56d88572cb01c18bcfe1faded)

Change-Id: I04445f0cf9a1e85172b64d57df92eb7939ce2332