Top scroll locking works; bottom almost works, but has an odd offset.
Directional scroll locking now works; added stubs for scrolling camera across a camera-locked boundary.
Unstaged changes from last commit.
Flash-scrolling across locked-camera boundaries and a few bugfixes.
Fixed the camera-desync bug (#1) for some situations.

This solution works when the player scrolls onto a locked axis when the camera isn't already locked on that axis.
The bug still exists in situations where the player scrolls off and back onto a locked axis.
Fixes a few more cases of bug #1, mostly relating to moving onto an empty screen.