fix Cython 3.0.0b1 warnings: default to C++11

setup.py

@@ -611,9 +611,14 @@ def ace(modnames="xpra.x11.bindings.xxx", pkgconfig_names="", optimize=None, **k
                 value = (value, )
             add_to_keywords(pkgc, addto, *value)
     pkgc.update(kwargs)
-    if WIN32 and kwargs.get("language", "")=="c++":
+    CPP = kwargs.get("language", "")=="c++"
+    if CPP:
+        #default to "-std=c++11" for c++
+        if not any(v.startswith("-std=") for v in pkgc.get("extra_compile_args", ())):
+            add_to_keywords(pkgc, "extra_compile_args", "-std=c++11")
         #all C++ modules trigger an address warning in the module initialization code:
-        add_to_keywords(pkgc, "extra_compile_args", "-Wno-error=address")
+        if WIN32:
+            add_to_keywords(pkgc, "extra_compile_args", "-Wno-error=address")
     add_cython_ext(modname, src, **pkgc)
 
 def tace(toggle, *args, **kwargs):