trivial: Silence some invalid _cleanup_free_ warnings
Don't assume pwd.h is always available
Don't assume syslog.h is always available
libcolord: Return correct values when no LUMINANCE_XYZ_CDM2 is specified
trivial: Do not require old-style dbus when specifying --disable-examples
Make the ArgyllCMS sensor driver optional

This doesn't make sense on platforms like RHEL which don't ship spotread.
trivial: Use EXEEXT when compiling tools used for compiling
Don't assume getuid() is available on all platforms
libcolord: Fix using cd_it8_add_spectrum() where the spectra have no ID values
trivial: Fix compile with --disable-gudev --enable-gusb
Fix compile using mingw64

Although I don't think colord makes a lot of sense on non-Linux platforms,
compiling for w64 seems to mean that we get a different set of compiler warnings
which benefits the Linux platform too.

Plus, the libraries might make sense on Windows one day.