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