Colors: we use constant colors everywhere

may as well make them convinient for everybody.
Label: take the string at construct time.
Control: really shouldn’t be setting ControlType outside the class.
GUI: remove redundant setting of Changed value.
use a slightly more direct means of obtaining GameControl
Use Polymorphisim for getting the text value of a control
Control: take the dimentions at construct time

also add a method to retrieve the dimentons as a Region
Interface: remove DrawConsole method

we can simply draw the console above all the windows without requireing the video driver to know anything about consoles
No point in drawing invisible windows
Control: factor out common draw code to base class
Control: setting focus should mark the control as changed
Control: make Changed private, add MarkDirty and NeedsDraw methods

Nothing should be able to unset Changed flag except when the control draws.
We seem to be overzealous about redrawing windows
TextArea: fix scrolling textareas being blank

also get rid of TA_BITEMYTAIL
TextArea: remove unused InternalFlags
GameControl: remove the touchscroll areas

it conflicts with multitouch input. If anybody complains we can reimplement in a better way, or preferably coax them into using multitouch.
Fix mixed up button states from 2461f42
SDL2: fix brightness setting.
Merge branch 'master' of github.com:gemrb/gemrb
SDL2: its starting to seem like all SDL2 platforms have the same pixel format

untested on Linux, and OS X hasnt been tested with SDL2 since before these changes.