Android 5.1.1 release 9
Merge changes Icedbb451,I57fac759,I2734a701,Ib0764206,Ic588b205, ...
* changes:
Merge remote-tracking branch 'strace/master' into HEAD
xtensa: sort values in struct_user_offsets
Document -k option as experimental
tests: robustify -k test
tests: enhance -k test
unwind: ignore memory mappings that have no PROT_EXEC bit set
unwind: cleanup build_mmap_cache
unwind: remove unused field from mmap_cache_t
unwind: refactor stacktrace_walk
unwind: constify binary_filename and symbol_name functions arguments
unwind: disable stack trace with multiple personalities