varLib. Add support for building CFF2 variable font with a call to varLib.build().

Fix bug in psCharStrings, to allow the CFF2Subr calls draw function to work

Lib/fontTools/misc/psCharStrings.py

@@ -1211,6 +1211,13 @@ class T2CharString(object):
 class CFF2Subr(T2CharString):
 	isCFF2 = True
 
+	def draw(self, pen):
+		subrs = getattr(self.private, "Subrs", [])
+		extractor = self.outlineExtractor(pen, subrs, self.globalSubrs,
+				0, 0)
+		extractor.execute(self)
+		self.width = 0
+
 class T1CharString(T2CharString):
 
 	operandEncoding = t1OperandEncoding