Auto merge of #1266 - torkleyy:point-size, r=kvark
Auto merge of #1266 - torkleyy:point-size, r=kvark

Only enable PROGRAM_POINT_SIZE for desktop

In OpenGL ES, it is enabled by default
and the flag is not supported.

ColinKinloch/gfx,davll/gfx,gfx-rs/gfx-rs,ColinKinloch/gfx