configitems: register the 'worker.backgroundclosemaxqueue' config

mercurial/configitems.py

@@ -155,3 +155,6 b" coreconfigitem('ui', 'interactive',"
 coreconfigitem('ui', 'quiet',
     default=False,
 )
+coreconfigitem('worker', 'backgroundclosemaxqueue',
+    default=384,
+)

mercurial/vfs.py

@@ -550,7 +550,7 b' class backgroundfilecloser(object):'
 
         # Windows defaults to a limit of 512 open files. A buffer of 128
         # should give us enough headway.
-        maxqueue = ui.configint('worker', 'backgroundclosemaxqueue', 384)
+        maxqueue = ui.configint('worker', 'backgroundclosemaxqueue')
         threadcount = ui.configint('worker', 'backgroundclosethreadcount', 4)
 
         ui.debug('starting %d threads for background file closing\n' %