Implement name_to_handle_at and open_by_handle_at syscalls decoding

Implement name_to_handle_at and open_by_handle_at syscalls decoding

* file_handle.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* linux/dummy.h (sys_name_to_handle_at, sys_open_by_handle_at):
Remove stub aliases.
* pathtrace.c (pathtrace_match): Add SEN_name_to_handle_at.
* tests/file_handle.c: New file.
* tests/file_handle.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add file_handle.
(TESTS): Add file_handle.test.
* tests/.gitignore: Add file_handle.