Ping**(5./7.) [patch, fortran] Implement maxval for characters

[Thomas Koenig]

Am 28.11.2017 um 19:40 schrieb Thomas Koenig:

Hello world,

the attached patch implements maxval for characters, an F2003 feature
that we were missing up to now.

Regression-tested on x86_64-pc-linux-gnu.

OK for trunk?

Ping?