[fortran,patch] Wide chars part 3 + fix PR36162 (null char in module string)

[Tobias Burnus]

Hi FX,

> This is a small third part of wide characters support, allowing us to
> read/write wide character strings in module files: we do that by
> quoting character strings:

> Bootstrapped and regtested on x86_64-linux (-m32 regtest is finished,
> -m64 is in progress), will come with the testcase from the PR. OK to
> commit?
OK.

(Though I wonder whether it makes sense to add a test case, e.g. based
on the one in the PR.)

Tobias