WIP: Use Mesa on Appveyor
FIX: Better testing
FIX: Skip bad mesa test
FIX: Fix font test
FIX: Update URL
FIX: Fix env var
FIX: 32-bit as well
FIX: Comment
FIX: Fix call
FIX: Revert to 64-bit only
ENH: Add 32-bit
FIX: Always try 64-bit?
FIX: Only use 32-bit
FIX: Fix check
Merge pull request #668 from Eric89GXL/mesa-win

ENH: Use Mesa on Appveyor
glir: Don't draw when count is zero

Fixes issue #661
Refactoring of GLIR queues: 1 on each canvas.context

So now there is a queue on each gloo object, which is kept there.
The queue can be associated with other queues, creating a sort
of tree. This also got rid of the need for a shared queue.
Added shared context example
address review comments

also canvas(config, shared)
attempt to reduce segfaults