Several improvements to shaderProgram, see details:

Several improvements to shaderProgram, see details:

- shaderProgramSetGshInputPermutation() was added
- shaderInstanceGetUniformLocation() return type corrected
- shaderInstanceSetBool bug fixed (true/false were incorrectly mapped)
- shaderInstance now has bitmasks indicating which int/bool uniforms are
  used by int/bool constants in the DVLE
- shaderProgramUse() was revamped:
  - Shader unit setup/code/opdesc upload code was separated into a new
    function called shaderProgramConfigure()
  - shaderProgramUse() calls shaderProgramConfigure() and afterwards
    uploads DVLE constants
  - GPU wrappers that perform uniform management will want to use
    shaderProgramConfigure() instead of shaderProgramUse() and later
    read the shaderInstance uniform usage bitmasks to set the constants.