Add support for glutSetCursor function

That pull request implements the glutSetCursor function.
The following GLUT cursor types are supported : 
* GLUT_CURSOR_INFO
* GLUT_CURSOR_HELP 
* GLUT_CURSOR_WAIT
* GLUT_CURSOR_TEXT
* GLUT_CURSOR_CROSSHAIR
* GLUT_CURSOR_UP_DOWN
* GLUT_CURSOR_LEFT_RIGHT
* GLUT_CURSOR_TOP_SIDE
* GLUT_CURSOR_BOTTOM_SIDE
* GLUT_CURSOR_LEFT_SIDE
* GLUT_CURSOR_RIGHT_SIDE
* GLUT_CURSOR_TOP_LEFT_CORNER
* GLUT_CURSOR_TOP_RIGHT_CORNER
* GLUT_CURSOR_BOTTOM_RIGHT_CORNER
* GLUT_CURSOR_BOTTOM_LEFT_CORNER
* GLUT_CURSOR_NONE 
After looking at the FreeGLUT implementation, an application exists with error when providing an invalid cursor value.

What is the alternative here? Throwing an exception when the cursor value is invalid (as in glutGet) ?