PR93253 – Document BOZ changes, make it friendlier in legacy code
PR fortran/93253
* check.c (gfc_invalid_boz): Mention -fallow-invalid-boz
in the error message.
* gfortran.texi (BOZ literal constants): List another missing
extension and refer to -fallow-invalid-boz.
* lang.opt (fallow-invalid-boz): Also mention 'X' in the help text
as it is not covered by the previous wording.
* primary.c (match_boz_constant): Tweak wording such that it is
clear how to fix the nonstandard use.
PR fortran/93253
* fortran.dg/boz_7.f90: Updated dg-error.