Fix Phobos dependencies on autodecoding

[Walter Bright]

We don't yet have a good plan on how to remove autodecoding and yet provide 
backward compatibility with autodecoding-reliant projects, but one thing we can 
do is make Phobos work properly with and without autodecoding.

To that end, I created a build of Phobos that disables autodecoding:

https://github.com/dlang/phobos/pull/7130

Of course, it fails. If people want impactful things to work on, fixing each 
failure is worthwhile (each in separate PRs).

Note that this is neither trivial nor mindless code editing. Each case has to be 
examined as to why it is doing autodecoding, is autodecoding necessary, and 
deciding to replace it with byChar, byDchar, or simply hardcoding the decoding 
logic.