Merge pull request #20 from metajack/mem-leak

Cast gfx::FontOptions before delete to fix memory leak.
Add FBO backed draw targets.

This adds support for Skia FBO draw targets to the C API as well as several
helper functions to create and manage the relevant contexts.
Restrict FBO support to mac.

This is only until shared GL context support is added to Skia for other platforms.
Merge pull request #21 from metajack/gpu-rendering

Add FBO draw target support
fix servo #472: rust-azure target doesn't depend on libskia.a
Add some high level bindings
Merge pull request #23 from sonwow/hl-bindings

Add some high level bindings
Merge pull request #22 from aydinkim/master

fix servo #472
Delete unused variable.
Enable debugging output.
Add dependencies on layers and opengles.
Implement TextureManager.
Remove spurious debugging.
Initialize GL context with a size.
Remove unused import.
Remove unneeded to_unsafe_ptr()s.
Remove skia debugging.
Merge pull request #24 from metajack/gpu-rendering

Gpu rendering
Remove Mac ifdefs now that Skia has linux support.
Merge pull request #26 from metajack/linux-gpu

Enable Skia GL on all platforms