Remove support for GLSL 1.10.

In practice, we haven't _actually_ supported this since we used integers
in ResampleEffect (and ResampleEffect is a pretty central effect),
so let's be honest with ourselves. (Also, we will soon start using arrays
in some cases, which are cumbersome pre-1.30.) I don't know of any drivers
that support all the other stuff we want but not GLSL 1.30 anyway;
it came with OpenGL 3.0, in 2008.

This actually isn't an ABI break, at least not on the C++ level.