Native bindings to the EXT_raster_multisample extension.

This extension allows rendering to a non-multisample color buffer while rasterizing with more than one sample. The result of rasterization (coverage) is available in the gl_SampleMaskIn[] fragment shader input, multisample rasterization is enabled for all primitives, and several per- fragment operations operate at the raster sample rate.

When using the functionality provided by this extension, depth, stencil, and depth bounds tests must be disabled, and a multisample draw framebuffer must not be used.

A fragment's "coverage", or "effective raster samples" is considered to have "N bits" (as opposed to "one bit" corresponding to the single color sample) through the fragment shader, in the sample mask output, through the multisample fragment operations and occlusion query, until the coverage is finally "reduced" to a single bit in a new "Coverage Reduction" stage that occurs before blending.

Requires GLES 3.0.