(svn r1894) - Codechange: cleaned up the console a bit, wholly unified handling of text with that of editboxes

- Codechange: Introduction of Textbuf struct which not only holds physical data as length but also pixel-constrains (width) and information about the caret
- Codechange: Move Clipboard function to OS specific file. Currently only Windows has clipboard actions
- Feature: Editboxes, console and exit screen also accept the numeric-enter as a yes
- Feature: Navigation through text with cursor keys is possible, as well as arbitrary insertion (also paste) and deletion; both backspace and del keys. Functions DeleteTextBufferChar, InsertTextBufferChar and InsertTextBufferClipboard handle input and deletion. Navigation is done through MoveTextBufferPos.
- Fix: OTTD crash when opening 'add server' editbox
- CodeChange: fix up some stringwidth calculations in gfx.c. You can get the width in pixels of a character by calling GetCharacterWidth().

unix.c

@@ -1,5 +1,6 @@
 #include "stdafx.h"
 #include "ttd.h"
+#include "window.h"
 #include "string.h"
 #include "table/strings.h"
 #include "hal.h"
@@ -525,3 +526,4 @@ void DeterminePaths(void)
 	mkdir(_path.scenario_dir, 0755);
 }
 
+bool InsertTextBufferClipboard(Textbuf *tb) {return false;}