revset: changed __add__ methods on lazy sets to return addsets (issue4191)

Performance Benchmarking:

$ hg --time log --graph --style compact --limit 6 -r 'sort((::. or bookmark()
or heads(public())), "-rev")'
time: real 1.540 secs (user 1.510+0.000 sys 0.020+0.000)

$ ./hg --time log --graph --style compact --limit 6 -r 'sort((::. or
bookmark() or heads(public())), "-rev")'
time: real 1.240 secs (user 1.190+0.000 sys 0.040+0.010)

mercurial/revset.py

@@ -2236,14 +2236,7 b' class lazyset(object):'
         return lazyset(self, lambda r: r not in x)
 
     def __add__(self, x):
-        def iterates():
-            for r in self:
-                yield r
-            for r in x:
-                if r not in self:
-                    yield r
-
-        return lazyset(generatorset(iterates()))
+        return lazyset(addset(self, x))
 
     def __nonzero__(self):
         for r in self:
@@ -2476,14 +2469,7 b' class spanset(object):'
             return orderedlazyset(self, lambda r: r not in x, ascending=False)
 
     def __add__(self, x):
-        def iterates():
-            for r in self:
-                yield r
-            for r in x:
-                if r not in self:
-                    yield r
-
-        return lazyset(generatorset(iterates()))
+        return lazyset(addset(self, x))
 
     def __len__(self):
         if not self._hiddenrevs: