libmount: fix gtk-doc comments and declarations

libmount: fix gtk-doc comments and declarations

- add LIBMOUNT_DISABLE_DEPRECATED guards around deprecated function
  declarations (mnt_optstr_apply_flags, mnt_has_regular_mtab,
  mnt_get_mtab_path)
- move mnt_table_enable_noautofs() and mnt_table_is_noautofs()
  declarations from private mountP.h to public libmount.h.in,
  convert doc comments to gtk-doc format
- fix missing colons in struct doc comments (libmnt_update,
  libmnt_context, libmnt_monitor, libmnt_statmnt)
- fix @id -> @ns parameter name in mnt_table_listmount_set_ns() doc
- fix typo mnt_table_fetch_listmont -> mnt_table_fetch_listmount
- fix wrong cross-references mnt_fs_set_ns_id() -> mnt_fs_set_ns(),
  mnt_table_fetch_statmount() -> mnt_fs_fetch_statmount()
- fix "Since: v2.42" -> "Since: 2.42" in mnt_monitor_enable_mountinfo

Signed-off-by: Karel Zak <kzak@redhat.com>