[Tools] Eliminate default value modification

LGTM catches a potential error with the mutation of default values:
implement their suggested workaround of using a None placeholder to
ensure the default itself is never modified.

src/Tools/generateBase/generateTools.py

@@ -100,12 +100,15 @@ def repl(match, self=self):
                 except TypeError:
                     self.ouf.write(self.regex.sub(repl, line))
                 i=i+1
-    def __init__(self, regex=_never, dict={},
+    def __init__(self, regex=_never, dict=None,
             restat=_never, restend=_never, recont=_never, 
             preproc=identity, handle=nohandle, ouf=sys.stdout):
         "Initialize self's attributes"
         self.regex   = regex
-        self.globals = dict
+        if dict is not None:
+            self.globals = dict
+        else:
+            self.globals = {}
         self.globals['sys'] = sys
         self.locals  = { '_cb':self.copyblock }
         self.restat  = restat