[RFC] -Weverything

[Thomas König]

> Am 23.01.2019 um 12:36 schrieb Jonathan Wakely <jwakely.gcc@gmail.com>:
> 
> When there are new warnings that aren't enabled by -Wall -Wextra,
> there's probably a reason they aren't enabled by default.

-Wconversion-extra is an example of such a warning.

It catches a very common error people make in Fortran, see https://gcc.gnu.org/ml/fortran/2019-01/msg00178.html for a false bug report which it would have caught early.

We left it out of -Wextra because people felt it was too noisy.