Fixes breakage of non-ASCII characters, regression from commit
cc72ceb3

Fixes https://github.com/MusicPlayerDaemon/MPD/issues/842

Optimizes a few nanoseconds from the common code path.

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

Fixes buffer overflow bug.

Fixes buffer overflow bug.

MPD handles all strings in UTF-8 internally.  Those decoders which
read Latin-1 tags are supposed to implement the conversion, instead of
passing Latin-1 to TagBuilder::AddItem().  FixTagString() is simply
the wrong place to do that, and hard-coding Latin-1 is kind of
arbitrary.