Ship depots exceed canals

[Rito13]

Actual result

Ship depot when build at the edge of canal looks both like it was over it and inside of it.

Expected result

The canal edge is drawn like it is inside the depot?

Or like in the OpenGFX1 ship depots do not exceed canals.

[zephyris]

Two issues:

• Vertical alignment of the OGFX2 ship depots are 1px too low.
• The OGFX2 canals have a 3D illusion (the railing and canal wall).
  I think it's mostly not fixable without giving up on the three dimensionality of the canals... Though the alignment can be tweaked by 1px.