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/message.c b/windows/message.c
index 1f799f1..1723efd 100644
--- a/windows/message.c
+++ b/windows/message.c
@@ -10,6 +10,7 @@
 #include <sys/time.h>
 #include <sys/types.h>
 
+#include "wine/winbase16.h"
 #include "message.h"
 #include "winerror.h"
 #include "win.h"