glamor fixes for 1.17 branch

[Adam Jackson]

On Thu, 2015-10-22 at 15:52 +0900, Michel Dänzer wrote:

> please consider backporting the following glamor fixes to the 1.17 branch:
> 
> 732e3b9c08532f40656010eac9d128601cc88c3f ("Instead of one
> glTexSubImage2D call for each glyph.") (May want to add back the
> original shortlog, "glamor: Use a single glTexImage2D call for core font
> atlas texture data v2", which was dropped when the patch was applied)
> 
> 1a18513a4eb3fa22459dd9f7d8f0e275aff679ec ("glamor: Use
> glamor_prepare_access_box() for PutImage/GetImage fallback")
> 
> db5337afb248edf81087cf8d74006fc496d70589 ("glamor: make current in
> prepare paths")
> 
> 0a458a908ec071a4da5d22c760581e0c5ec885ce ("glamor: Make our EGL context
> current before calling into GL in glamor_init")

Cherry-picked these to 1.17 branch, thanks.

- ajax