Make CppHeaderParser script ignore "using" statements

- It doesn't handle them properly and instead assumes they're
  an ivar.
Make IDE build on OSX when 10.6 SDK isn't available

- More recent versions of Xcode no longer ship with the
  10.6 SDK so the default SDK setting of 10.6 causes an
  error. This change makes it build with whatever is
  the latest SDK on whatever Xcode is being used
  but sets the deployment target to 10.6 so that it
  will run there as well.
Add Vector2 version of hitTest()
Make initial hitBox size match initial width/height

- Otherwise it's possible to have a clickable entity
  with zero size by default which seems like something
  you don't want as a default behavior.
Make sure all UIElements descend from UIElement

- This way they all get the same default positionMode
  since they're all positioned as if they're TOPLEFT
  but these UI classes weren't descended from UIElement
  so their default positionMode was CENTER. It just
  happened to work because they themselves weren't
  displayed. Fixing this provides the knowledge needed
  to produce a proper concatenated screen position matrix.
Remove redundant removeAllHandlersForListener() in dtor

- Already called at top of method.
Remove need for parentAdjust in _onMouse*() methods

- hitTest can now be used without parentAdjust.
- Make getScreenConcatenatedMatrix() to return a matrix
  that can be used to produce screen coordinates.
- Rename local "transformMatrix" variable to "screenMatrix"
  so we're not hiding the "transformMatrix" ivar.
Add definition to suppress min/max macros on Windows

- When you include windows.h it will define a pair
  of min/max macros. This becomes a problem when you
  want to use the min/max defined as templates in
  <algorithm>. The templates are preferred as you
  only calculate the values of the arguments once
  rather than the two times that the macro does.
Add Clipped() method to Rectangle with some edge methods

- Added Clipped() which returns the rectangle clipped by
  the bounds of the passed-in rectangle.
- Also added some convenience methods for getting the
  locations of the rectangle edges. Helps bring a litte
  clarity and the max*() methods are especially useful
  as that is a not uncommon operation. I included
  the min*() methods for completeness so if you're
  working with edges your code will read consistent
  although I don't mind if people would rather they
  were deleted.
Add == and != operators to Rectangle class
Use Rectangle's new Clipped() method for scissorBox

- Fix bug/oddity with scissor rects. What looked like it was
  clipping children by their parent's scissor rect was clipping
  the min but when clipping the max was using the new min edge
  to calculate the old max edge thus making the clipping rect
  too large. This seemed to work because we were having children
  clip themselves and the text editor was the only thing
  really using the scissor functionality.
- Set Renderer's initial scissor rect via the setter so that
  later calls to getScissorBox() will return the correct value.
- Make scroll containers clip their children rather than having
  them set their children to be clipped.
- Only make UITextInput's textContainer clip on single-line input
  because its size isn't set properly to be used to clip with.
Use setPositionMode() accessor when possible

- Gives some extra flexibility if things need to
  happen when this changes.
Make some ScreenEntity methods const
Fix some indentation in ScreenEntity

- This code was hard for me to follow without
  consistent intendation.
Add "const" to a number of methods

- mostly Clone() and applyClone() methods, which required
  changing Entity which then required touching everything
  that overrode those methods.
- I just wanted to add const to all the obvious methods in
  ScreenEntity but then I touched Clone() and I had to touch
  everything.
Remove unused variables to fix some warnings

- Found on OS X.
Remove dumpstack() as it was unused

- I'm falling back on the "if someone wants it, they
  know where to find it" argument.
- This fixes an "unused function" warning on OS X.
Fix "unused variable" warnings found on OS X

- Someone should probably double-check that I didn't
  remove an important function call but most of it was
  getting the font size which was never used.
Fix "not all enum values used in switch" warning on OS X

- Just added a "defaut:" case so the compiler knows
  we've got it handled.
Fix "unknown message" warning on OS X

- Forward declare the AppDelegate class, give the appDelegate
  pointer a specific type and move the handleEvent method
  into the .m file.
- The whole class definition could have been moved below
  the AppDelegate class definition and I wouldn't have had to
  bother with putting things in the .m file but this felt
  a little better (six of one, half-dozen of the other *shrug*).