fix, PEBKAC, assign tm_sec, tm_min, tm_hour in ffff_gmtime() properly
hygiene, use ffff_gmtime()'s hour, min, sec slots for dt_datetime()
chore, go easy on the number of ipo object files, use heuristics
chore, prefer xild for linking over ld
chore, only go for -ipo enabled ar/ld (xiar/xild) when -ipo is accepted by the compiler
chore, kick warnings about ansi-aliasing violations
chore, pass some of the diags on to the linker
chore, move anti-aliasing warnings for xild/xiar to FEATFLAGS
chore, pass -ipo on to the linker
Merge branch 'code/hygiene'

* code/hygiene:
  chore, pass -ipo on to the linker
  chore, move anti-aliasing warnings for xild/xiar to FEATFLAGS
  chore, pass some of the diags on to the linker
  chore, kick warnings about ansi-aliasing violations
  chore, only go for -ipo enabled ar/ld (xiar/xild) when -ipo is accepted by the compiler
  chore, prefer xild for linking over ld
  chore, go easy on the number of ipo object files, use heuristics
  hygiene, use ffff_gmtime()'s hour, min, sec slots for dt_datetime()
  fix, PEBKAC, assign tm_sec, tm_min, tm_hour in ffff_gmtime() properly