chore, check for dfp754 decimal funs

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, ask for gnu11 or gnu99 standard (we need typeof)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, import dfp754 implementations of stuff that we need (courtesy of cattle)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'feat/dfp754'

* feat/dfp754:
  minor, import dfp754 implementations of stuff that we need (courtesy of cattle)
  chore, ask for gnu11 or gnu99 standard (we need typeof)
  chore, check for dfp754 decimal funs