feature(wayland): Add a shared memory manager.

[ghost]

Allowing backing buffers to be allocated on demand. In addition, the shared memory manager tracks buffer acquisition history (in Wayland EGL parlance 'buffer age'), allowing the acquiring code to perform a delta initialization (apply changes from previously acquired buffers to the most recent, as oppose to a full buffer initialization).
In particular, the shared memory manager, maintains a shared memory pool, wherein individual buffers, belonging to separate buffer groups (which all have the same size) are allocated from. A LRU cache is then used on top of this to keep a hot cycle (i.e. swap chain) available. Finally, the acquiring code, caches individual buffer damage in a ring buffer to be able to apply the aforementioned delta initialization.

This PR is my completion of the work started in #250.

Notes:

• There's some toggles implemented (namely the ring buffer size and shared memory manager preferred number of buffers), which can be changed to tradeoff swap-chain length (and thus delta initialization time) and allocation overhead.
• Still a lot of places where performance could be improved (and heuristics added), in particular the ring buffer could use a weighted size to make a decision of when to delta initialize or full initialize a buffer
• This implementation has mostly been hacked on to the existing Wayland driver, to hopefully fix-up a couple bugs/make it more Wayland conformant
• Moving forward I may look to implement the SHM interface backend on SDL, as I believe with this the SDL driver would be feature superior to this driver

[kisvegabor]

Thank you very much @simplejack-src. Can I merge it or are we waiting feedback from someone?

[ghost]

It works for me(TM) :). @WallaceIT see anything out of place?

[WallaceIT]

Seems very well done! I don't have time nor means to test it since I'm travelling, though.

[kisvegabor]

Thanks for taking a look @WallaceIT.

I'll merge it now then. Please open a new issue if you find an issues later.