issue #155: fork: nop out get_boot_command, it's become quite expensive

-16% reduction in fork cost.

mitogen/fork.py

@@ -70,7 +70,7 @@ class Stream(mitogen.parent.Stream):
 
     name_prefix = 'fork'
 
-    def create_child(self, *_args):
+    def start_child(self):
         parentfp, childfp = mitogen.parent.create_socketpair()
         self.pid = os.fork()
         if self.pid:

mitogen/parent.py

@@ -442,9 +442,12 @@ class Stream(mitogen.core.Stream):
     create_child = staticmethod(create_child)
     name_prefix = 'local'
 
+    def start_child(self):
+        return self.create_child(*self.get_boot_command())
+
     def connect(self):
         LOG.debug('%r.connect()', self)
-        self.pid, fd = self.create_child(*self.get_boot_command())
+        self.pid, fd = self.start_child()
         self.name = '%s.%s' % (self.name_prefix, self.pid)
         self.receive_side = mitogen.core.Side(self, fd)
         self.transmit_side = mitogen.core.Side(self, os.dup(fd))