add ColorFromInt for convenance

[danilwhale]

because there's ColorFromNormalized -> ColorToNormalized, ColorFromHSV -> ColorToHSV

but GetColor -> ColorToInt, not ColorFromInt -> ColorToInt

[Peter0x44]

This is inconsistent.
GetColor returns int, while ColorToInt takes an unsigned int.
I think these functions are a little broken anyway, since the exact representation of (unsigned) int depends on endianness.
Probably they deserve a deeper review.

also, nit: convenance -> convenience.
At least I assume that's what you meant, "convenance" is not a thing.

[raysan5]

@danilwhale I prefer to avoid that function duplicate, despite the consistency it could add. Same behaviour can be accomplished with a #define GetColor ColorFromInt but probably as @Peter0x44 commented all those functions mentioned should be reviewed, I don't like the reference to a specific language data type in the name of the functions, that's counter-productive for other language bindings. Naming for those functions should be reviewed.