4.5 Status of Fortran 2018 support

So far very little work has been done to support Fortran 2018.

• ERROR STOP in a PURE procedure An ERROR STOP statement is permitted in a PURE procedure.
• IMPLICIT NONE with a spec-list Support the IMPLICIT NONE statement with an implicit-none-spec-list.
• Behavior of INQUIRE with the RECL= specifier

  The behavior of the INQUIRE statement with the RECL= specifier now conforms to Fortran 2018.