Optimized include/*.h: (recursively) include all headers needed by
this .h file, but only those. Necessary fixes to a lot of .c files,
started optimizing "windows.h" away from some of them. Moved
GetCurrentTask prototype to wine/winbase16.h.

diff --git a/windows/win.c b/windows/win.c
index 01b2131..202b8ff 100644
--- a/windows/win.c
+++ b/windows/win.c
@@ -8,6 +8,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include "wine/winbase16.h"
 #include "options.h"
 #include "class.h"
 #include "win.h"