RFC: include: Add '_ONCE' variants of DPRINTF, FIXME, WARN and ERR

[Dan Kegel]

How about this:

#define WINE_ONCE(x) { static int wine_once_var##__LINE__; if
(!wine_once_var##__LINE__++) { x; }}

Example use:

-    static int once;
-    if (!once++) FIXME_(keyboard)("(%p,%d,0x%08x,%X):
stub\n",hwnd,id,modifiers,vk);
+    WINE_ONCE(FIXME_(keyboard)("(%p,%d,0x%08x,%X):
stub\n",hwnd,id,modifiers,vk));