libcolord: Add helpers for getting int and double values from the DOM tree
trivial: Rebuild the sRGB profile if the XML changes
libcolord: Load the profile rather than just setting the internal instance

We need to parse the profile to identify it as a V4 profile.
Never promote localized v2 ICC profiles to v4 when writing locale data

Doing this isn't a good idea, and we can achieve the same result using an Apple
extension that LCMS2 and colord now understand.
trivial: Fix build warning on OpenBSD

Rename gamma as this is helpfully defined by /usr/include/math.h