Bitmap: Use more accurate HSV-based hue shift algorithm

The previously YIQ-based algorithm turned out to be both slow,
and horribly inaccurate.

Another algorithm based on rotating the color value in the
RGB cube along the diagonal axis was also considered, which was
acceptable in terms of accuracy, and very fast.

In the end, I decided on a HSV-based one, because it is by far
the most accurate one, while still being a tad faster than the
YIQ solution.
Algorithm source: gamedev.stackexchange.com/a/59808/24839

A very simple GPU time benchmark when shifting a 2048^2 bitmap:

         YIQ rot   RGB rot   HSV shift
radeon   13.4 ms   2.8 ms    11.4 ms
intel    13.0 ms   6.0 ms    10.5 ms

radeon: HD 3650 mobility
intel:  N3540 integrated (Baytrail)

However hue shifting has never shown up as a bottleneck before,
so these are more academic.

src/shader.cpp

@@ -551,7 +551,6 @@ HueShader::HueShader()
 	ShaderBase::init();
 
 	GET_U(hueAdjust);
-	GET_U(inputTexture);
 }
 
 void HueShader::setHueAdjust(float value)
@@ -559,11 +558,6 @@ void HueShader::setHueAdjust(float value)
 	gl.Uniform1f(u_hueAdjust, value);
 }
 
-void HueShader::setInputTexture(TEX::ID tex)
-{
-	setTexUniform(u_inputTexture, 0, tex);
-}
-
 
 SimpleMatrixShader::SimpleMatrixShader()
 {