Renaming for consistency.
Change the output directory for 64-bit VC12 build.
GUI: Improve the way the relative positions of elements are updated.

This commit also fixes an issue where the absolute positions were not getting calculated.
GUI: Improvements to rendering.

With this commit, painting the GUI is done on a per-surface basis. In addition, the
foundations for a cleaner clipping have been put in place. This has not yet been
fully tested.
GUI: Improve the way the positions of auto-positioned elements are calculated.
GUI: Improve support for min/max sizing.
GUI: Add the infrastructure for borders.
GUI: Rename some variables for consistency.
GUI: Work on validating the layouts of elements in response to the inner width of an element changing.
GUI: Use floating point variables in calculating clipping.
GUI: Add style data for padding and margins.
GUI: A heap of changes and improvements to the layout system.
Remove some dead code.
GUI: Improve support for setting the boundary of relative dimensions of children.

This commit also fixes a bug with the way the border colours are retrieved.
GUI: Add some files for helping with logging.
GUI: Code cleanup and improved element positioning style support.
GUI: Remove the notion of a default surface.
Add stb_image.
More misc. GUI work.
Add the foundations for fonts/text to the new GUI system.