Drop support of dummy members of struct stat

Drop support of dummy members of struct stat

As st_flags, st_fstype, and st_gen members of struct stat are not filled
by the kernel, there is no use supporting them.

* configure.ac (AC_CHECK_MEMBERS): Remove struct stat.st_flags,
struct stat.st_fstype, and struct stat.st_gen.
* file.c [STAT32_PERSONALITY, HAVE_STRUCT_STAT64]: Do not undefine
HAVE_STRUCT_STAT_ST_FLAGS, HAVE_STRUCT_STAT_ST_FSTYPE,
and HAVE_STRUCT_STAT_ST_GEN.
* printstat.h (DO_PRINTSTAT): Do not check for
HAVE_STRUCT_STAT_ST_FLAGS, HAVE_STRUCT_STAT_ST_FSTYPE,
and HAVE_STRUCT_STAT_ST_GEN.