WIP: Fix shader compilation on hardware that doesn't support GLSL 1.30

In particular this affects pre-2011 Intel GPUs (5th generation, "Ironlake", or older). It also affects Nvidia hardware older than Geforce 8xxx and AMD/ATI Radeon hardware older than Radeon HD, but those are from 2006 and 2007 respectively, so older generations are probably no longer relevant.

Hopefully Closes: #923226, testing on old hardware required. (@jpuydt?)