[patch, Fortran] Fix PR 82372

[Thomas Koenig]

Hello world,

the attached patch displays an error for characters which are
outside the normal Fortran character set, and includes a hex
code when it is not printable.

gfortran 4.9 did display unprintable characters in the file,
so it might be argued that this bug is a regression.

Regression-tested. OK for trunk? What do people feel about backporting?

Regards

	Thomas

2017-10-10  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/82372
         * fortran/scanner.c (valid_chars): String with all characters
         which could be valid in Fortran.
         (valid_table):  Boolean table to select valid characters.
         (gfc_scanner_init_1): Set up valid_table from vaid_chars.
         (gfc_gooble_whitespace): If a character not in the Fortran
         character set appears, display error.

2017-10-10  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/82372
         * gfortran.dg/illegal_char.f90: New test.
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