Only expose :accuracy and :reduction if !i386, similar to before,
but more holistically to avoid future -Wunused issue with the unused
functions.
r321484:
Only test ld_pi_odd with LDBL_MANT_DIG == 64 to fix the build
The empty (unimplemented) test inputs for sparc64 trigger a -Wtype-limits build
failure because nitems of an empty array is always false, i.e., deadcode.