llvmpipe: bump glsl version to 140

llvmpipe: bump glsl version to 140

texel offsets should have been the last missing feature for 130, and in
fact 140 as well (last there were texture buffers). In any case we still
don't do OpenGL 3.0 (missing MSAA which will be difficult,
plus EXT_packed_float, ARB_depth_buffer_float and EXT_framebuffer_sRGB).

v2: bump to 140 instead - we have everything except we crash when not writing
to gl_Position (but softpipe crashes as well) so let's just say this is a bug
instead. Also (by Dave Airlie's suggestion) update llvm-todo.txt.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>