kmssink: add support for GBM allocator

Submitted by Randy Li (ayaka)

Link to original bug (#796493)

Description

Created attachment 372542
allocator

In the Android, there is a similiar usuage with GPU memory, it use galloc() to allocate and access a memory from GPU.
There is a GBM support in -base, it doesn't include any memory operation.

This patch is verified with ARM MALI GPU library.

Patch 372542, "allocator":
0003-kms-gbm-add-a-new-gbm-allocator.patch