[gvar] Remove GlyphCoordinates.__abs__()

It's not wel-defined, as abs typically is supposed to return a scalar...

Also combine the tolerance-check with the zero-check in varLib.

Lib/fontTools/ttLib/tables/_g_l_y_f.py

@@ -1355,22 +1355,6 @@ class GlyphCoordinates(object):
 		for i in range(len(a)):
 			a[i] = -a[i]
 		return r
-	def __abs__(self):
-		"""
-		>>> g = GlyphCoordinates([(-1.5,2)])
-		>>> g
-		GlyphCoordinates([(-1.5, 2.0)])
-		>>> g2 = abs(g)
-		>>> g
-		GlyphCoordinates([(-1.5, 2.0)])
-		>>> g2
-		GlyphCoordinates([(1.5, 2.0)])
-		"""
-		r = self.copy()
-		a = r._a
-		for i in range(len(a)):
-			a[i] = abs(a[i])
-		return r
 	def __round__(self):
 		"""
 		Note: This is Python 3 only.  Python 2 does not call __round__.

Lib/fontTools/varLib/__init__.py

@@ -232,6 +232,8 @@ def _optimize_delta(delta, coords, ends):
 
 def _add_gvar(font, model, master_ttfs, tolerance=.5, optimize=True):
 
+	assert tolerance >= 0
+
 	log.info("Generating gvar")
 	assert "gvar" not in font
 	gvar = font["gvar"] = newTable('gvar')
@@ -261,9 +263,7 @@ def _add_gvar(font, model, master_ttfs, tolerance=.5, optimize=True):
 		endPts = control[1] if control[0] >= 1 else list(range(len(control[1])))
 
 		for i,(delta,support) in enumerate(zip(deltas[1:], supports[1:])):
-			if all(0 == v for v in delta.array):
+			if all(abs(v) <= tolerance for v in delta.array):
-				continue
-			if tolerance and max(abs(delta).array) <= tolerance: # XXX
 				continue
 			var = TupleVariation(support, delta)
 			if optimize: