New API: xfs_info2

Reimplement xfs_info by returning a hash table of values (rather than
a limited struct), and by writing it in OCaml with PCRE which makes
string parsing a lot simpler.  This will now flexibly return all the
fields from the underlying xfs_info command, even (hopefully) future
fields.

Note the field values are returned as strings, because the actual
fields in xfs_info output are fairly random and free-form.  There is a
trade off here between returning as much information as we can, and
requiring the user to do a bit of (simple) field parsing.

Fixes: https://issues.redhat.com/browse/RHEL-143673

.gitignore

@@ -119,6 +119,7 @@ Makefile.in
 /daemon/stubs-?.c
 /daemon/stubs.h
 /daemon/types.ml
+/daemon/xfs.mli
 /depcomp
 /docs/guestfs-building.1
 /docs/guestfs-faq.1