Nightly build from 2022-01-04-02-09-52

Fix incorrect colour value interpretation in the FreeType renderer (#…

…536)

BIG_ENDIAN might be defined by system headers, and it apparently is on both
Linux and recent macOS versions. Get rid of this completely, replace the union
by a struct and use endianness-independent constructs to obtain the values of
individual colour channels.

Also fix some minor warnings in the renderer code.

Fixes #507.