ADDED: `rlUnloadShader()` to unload shaders (that function was missing and compute shaders leak memory)
RENAMED: `rlCompileShader()` to p `rlLoadShader()` to be consistent with `rlUnloadShader()`
RENAMED: `rlLoadShaderCode()` to `rlLoadShaderProgram()`, more descriptive of return
RENAMED: `rlLoadShaderProgram()` to `rlLoadShaderProgramEx()`
RENAMED: `rlLoadComputeShaderProgram()` to `rlLoadShaderProgramCompute()`
RENAMED: Some functions parameters for consistency