Emulate logiop on gles

All logicops are emulated when GL_EXT_framebuffer_fetch or GL_EXT_framebuffer_fetch_non_coherent are available. If non of these two extensions is available then only SET, CLEAR, COPY, and COPY_INVERTED are emulated.

This fixes the according tests of the piglit gl-1.0-logicop when run on a GLES host.