Add the ability for Sliders and their corresponding Screens to have the ability to move in steps greater than 1.
No float support, only the integer screens are affected.
Make sure the Slider can't step in increments of less than 1.
Use integers instead.
Add GL_NV_pixel_buffer_object that seen on Tegra platform
gl_extensions.PBO_NV = strstr(extString, "GL_NV_pixel_buffer_object") != 0;
Merge pull request #214 from raven02/patch-21

Add GL_NV_pixel_buffer_object that seen on Tegra platform
Merge pull request #213 from thedax/slider-stepping

Add the ability for integer-based Sliders and their corresponding Screens to have the ability to move in steps greater than 1.
Oops, make sure step_ is initialised, even with the constructor that doesn't specify a step.
Just to be safe, initialise the Slider's step_ too.
Merge pull request #215 from thedax/slider-bug-fix

Make sure step_ is initialised, even with the constructor that doesn't specify a step.
Load glBlitFramebufferNV extension correctly