re PR fortran/31675 (Fortran front-end and libgfortran should have a common header file)
PR fortran/31675
* libgfortran.h: New file.
* iso-fortran-env.def: Use macros in the new header instead of
hardcoded integer constants.
* Make-lang.in (F95_PARSER_OBJS, GFORTRAN_TRANS_DEPS): Add
fortran/libgfortran.h.
* gfortran.h (GFC_STD_*, GFC_FPE_*, options_convert,
ioerror_codes): Remove.
* trans.c (ERROR_ALLOCATION): Remove.
(gfc_call_malloc, gfc_allocate_with_status,
gfc_allocate_array_with_status): Use LIBERROR_ALLOCATION.
* trans-types.h (GFC_DTYPE_*): Remove.
* trans-decl.c (gfc_generate_function_code): Use
GFC_CONVERT_NATIVE instead of CONVERT_NATIVE.
* trans-io.c (set_parameter_value, set_parameter_ref): Use
LIBERROR_* macros instead of IOERROR_ macros.
* trans-intrinsic.c (gfc_conv_intrinsic_function): Use
LIBERROR_END and LIBERROR_EOR instead of hardcoded constants.
* options.c (gfc_init_options): Use GFC_CONVERT_NATIVE instead of
CONVERT_NATIVE.
(gfc_handle_option): Use GFC_CONVERT_* macros instead of CONVERT_*.