panoramiX: make XINERAMA_FOR_EACH_SCREEN_* macros variadic

The XINERAMA_FOR_EACH_SCREEN_FORWARD / _FORWARD_SKIP0 / _BACKWARD macros
took the loop body as a single macro parameter. Any top-level comma in
the body was therefore parsed as an argument separator, so a body
containing e.g. a designated initialiser (`Foo f = { .a = 1, .b = 2 };`)
failed to compile — the reason for the existing "static init would
confuse preprocessor" workarounds at the call sites.

Pass the body as a variadic argument (`...` / `__VA_ARGS__`) instead.
Commas in the body are then preserved, so ordinary designated
initialisers (and other comma-containing statements) can be used in the
loop body without compound-literal-cast or memset workarounds.

Pure enabling change: all existing call sites pass a single brace block,
which is unchanged as __VA_ARGS__. Build-verified (Xvfb/Xnest link).

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
(cherry picked from commit 486d71c5b0)

Xext/panoramiX/panoramiX.h

@@ -73,14 +73,18 @@ typedef struct {
  * Makes a new scopes and declares `walkScreenIdx` as the current screen's
  * index number as well as `walkScreen` as poiner to current ScreenRec
  *
- * @param __LAMBDA__ the code to be executed in each iteration step.
+ * The body is passed via a variadic parameter so it may contain top-level
+ * commas (e.g. a `Foo f = { .a = 1, .b = 2 };` designated initialiser)
+ * without being mis-parsed as multiple macro arguments.
+ *
+ * @param ... the code to be executed in each iteration step.
  */
-#define XINERAMA_FOR_EACH_SCREEN_FORWARD(__LAMBDA__) \
+#define XINERAMA_FOR_EACH_SCREEN_FORWARD(...) \
     do { \
         for (unsigned walkScreenIdx = 0; walkScreenIdx < PanoramiXNumScreens; walkScreenIdx++) { \
             ScreenPtr walkScreen = screenInfo.screens[walkScreenIdx]; \
             (void)walkScreen; \
-            __LAMBDA__; \
+            __VA_ARGS__; \
         } \
     } while (0);
 
@@ -88,29 +92,37 @@ typedef struct {
  * just like XINERAMA_FOR_EACH_SCREEN_FORWARD(), but skipping the first
  * screen (which is the frontend to the client)
  *
- * @param __LAMBDA__ the code to be executed in each iteration step.
+ * The body is passed via a variadic parameter so it may contain top-level
+ * commas (e.g. a `Foo f = { .a = 1, .b = 2 };` designated initialiser)
+ * without being mis-parsed as multiple macro arguments.
+ *
+ * @param ... the code to be executed in each iteration step.
  */
-#define XINERAMA_FOR_EACH_SCREEN_FORWARD_SKIP0(__LAMBDA__) \
+#define XINERAMA_FOR_EACH_SCREEN_FORWARD_SKIP0(...) \
     do { \
         for (unsigned walkScreenIdx = 1; walkScreenIdx < PanoramiXNumScreens; walkScreenIdx++) { \
             ScreenPtr walkScreen = screenInfo.screens[walkScreenIdx]; \
             (void)walkScreen; \
-            __LAMBDA__; \
+            __VA_ARGS__; \
         } \
     } while (0);
 
 /*
  * like XINERAMA_FOR_EACH_SCREEN_FORWARD(), but traveling backwards.
  *
- * @param __LAMBDA__ the code to be executed in each iteration step.
+ * The body is passed via a variadic parameter so it may contain top-level
+ * commas (e.g. a `Foo f = { .a = 1, .b = 2 };` designated initialiser)
+ * without being mis-parsed as multiple macro arguments.
+ *
+ * @param ... the code to be executed in each iteration step.
  */
-#define XINERAMA_FOR_EACH_SCREEN_BACKWARD(__LAMBDA__) \
+#define XINERAMA_FOR_EACH_SCREEN_BACKWARD(...) \
     do { \
         for (unsigned __walkidx = PanoramiXNumScreens; __walkidx > 0; __walkidx--) { \
             unsigned walkScreenIdx = __walkidx - 1; \
             ScreenPtr walkScreen = screenInfo.screens[walkScreenIdx]; \
             (void)walkScreen; \
-            __LAMBDA__; \
+            __VA_ARGS__; \
         } \
     } while (0);