fs_mgr: update ext4_parse_sb to match change in ext4_utils

ext4_parse_sb now takes the struct fs_info to fill out to avoid
using the global info from external callers.

Change-Id: I0984ba01c0dbdd5b68b825817faf0c5cf5aa5510
fs_mgr: split fstab parsing into separate file

Move fstab parsing into fs_mgr_fstab.c so that it compiles into a
separate compilation unit.  uncrypt links against it but doesn't
need to pull in the rest of the dependencies on fs_mgr.c.

Change-Id: I6bffe1cd42720151533e958028259d1931aaa4bf

Conflicts:
	fs_mgr/fs_mgr.c
Re-enable libunwind for arm.

Update to handle the new optimized way that libunwind works.

In addition, a small refactor of the BacktraceMap code.

A few new tests of for good measure.

Change-Id: I2f9b4f5ad5a0dfe907b31febee76e4b9b94fb76f

Conflicts:
	debuggerd/tombstone.cpp
	include/backtrace/Backtrace.h
	include/backtrace/BacktraceMap.h
	libbacktrace/Android.mk
	libbacktrace/BacktraceImpl.cpp
	libbacktrace/BacktraceImpl.h
	libbacktrace/BacktraceMap.cpp
	libbacktrace/BacktraceThread.cpp
	libbacktrace/BacktraceThread.h
	libbacktrace/Corkscrew.cpp
	libbacktrace/Corkscrew.h
	libbacktrace/UnwindCurrent.cpp
	libbacktrace/UnwindCurrent.h
	libbacktrace/UnwindPtrace.cpp
	libbacktrace/UnwindPtrace.h
	libbacktrace/backtrace_test.cpp