Move main executable source to its own directory (#248)

* Move main executable files to their own directory

* Adapt the build to the new file structure

... and fix some weird #include's that were relying on the project root
being an include directory.

Ja2/MPChatScreen.h

@@ -0,0 +1,29 @@
+#ifndef _MP_CHAT_SCREEN_H_
+#define _MP_CHAT_SCREEN_H_
+
+#include "MessageBoxScreen.h"
+
+UINT32	MPChatScreenInit( void );
+UINT32	MPChatScreenHandle( void );
+UINT32	MPChatScreenShutdown( void );
+
+extern CHAR16 gszChatBoxInputString[255];
+extern BOOLEAN gbChatSendToAll;
+extern MESSAGE_BOX_STRUCT	gChatBox;
+extern BOOLEAN	gfInChatBox;
+
+#define CHAT_FONT_COLOR		208 // WHITE
+
+////////////////////////////////
+// ubStyle:				Determines the look of graphics including buttons
+// zString:				16-bit string
+// uiExitScreen		The screen to exit to
+// ubFlags				Some flags for button style
+// ReturnCallback	Callback for return. Can be NULL. Returns any above return value
+// pCenteringRect	Rect to send if MSG_BOX_FLAG_USE_CENTERING_RECT set. Can be NULL 
+////////////////////////////////
+
+INT32 DoChatBox( bool bIncludeChatLog, const STR16 zString, UINT32 uiExitScreen, MSGBOX_CALLBACK ReturnCallback, SGPRect *pCenteringRect );
+void ChatLogMessage( UINT16 usColor, UINT8 ubPriority, STR16 pStringA, ...);
+
+#endif