[flang] Correct interpretation of RECL=

When RECL= is set on OPEN(), ensure that it:
  1) enforces a max output record payload size
     (not including header+footer or newline), and
  2) causes padding of short output records only
     for ACCESS='DIRECT'

The previous code was causing some false overrun errors
and applying padding to sequential/stream output files.

Differential Revision: https://reviews.llvm.org/D118630