Lowercase windows.h includes for MinGW cross-compiling compatibility

src/tools/cursors.win.cpp

@@ -1,6 +1,6 @@
 
 #include "cursors.hpp"
-#include <Windows.h>
+#include <windows.h>
 #include <exception>
 #include <SFML/Graphics/RenderWindow.hpp>
 #include "restypes.hpp"

src/tools/debugout.win.cpp

@@ -1,7 +1,7 @@
 
 #include <sstream>
 #include <iostream>
-#include <Windows.h>
+#include <windows.h>
 
 // Debugger streambuf adapted from here: <http://www.codeproject.com/Articles/1053/Using-an-output-stream-for-debugging>
 

src/tools/graphtool.cpp

@@ -13,7 +13,7 @@
 #include <OpenGl/GL.h>
 #else
 #ifdef _WIN32
-#include <Windows.h>
+#include <windows.h>
 #endif
 #include <GL/GL.h>
 #endif

src/tools/menu_accel.win.hpp

@@ -1,5 +1,5 @@
 
-#include <Windows.h>
+#include <windows.h>
 #include <vector>
 
 struct accel_table_t {

src/tools/winutil.win.cpp

@@ -1,7 +1,7 @@
 
 #include "winutil.hpp"
 #include <iostream>
-#include <Windows.h>
+#include <windows.h>
 #include <SFML/Graphics/RenderWindow.hpp>
 #include <SFML/Graphics/Image.hpp>
 #include <sstream>