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.

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

Use a boolean flag instead.

Avoid NaN to allow -ffast-math.

Avoid NaN to allow -ffast-math.

Don't require a writable string, and don't modify it.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Fixes build problems with mingw32.

Not a CPP macro.  This adds the "unused" attribute to "saveptr", which
eliminates one gcc warning.

Remove cross_fade_apply(), and call pcm_mix() in the output thread,
mixing the chunk and chunk->other together.

Adds mixrampdb and mixrampdelay commands.  Reads MIXRAP_START and
MIXRAMP_END tags from FLAC files and overlaps instead of crossfading.