Consolidate bit_count / popCount methods

Fixes https://github.com/fonttools/fonttools/issues/2331

Lib/fontTools/misc/intTools.py

@@ -1,28 +1,14 @@
 __all__ = ['popCount']
 
 
-def popCount(v):
+try:
-    """Return number of 1 bits (population count) of an integer.
+    bit_count = int.bit_count
+except AttributeError:
+    def bit_count(v):
+        return bin(v).count('1')
 
-    If the integer is negative, the number of 1 bits in the
+"""Return number of 1 bits (population count) of the absolute value of an integer.
-    twos-complement representation of the integer is returned. i.e.
-    ``popCount(-30) == 28`` because -30 is::
 
-        1111 1111 1111 1111 1111 1111 1110 0010
+See https://docs.python.org/3.10/library/stdtypes.html#int.bit_count
-
+"""
-    Uses the algorithm from `HAKMEM item 169 <https://www.inwap.com/pdp10/hbaker/hakmem/hacks.html#item169>`_.
+popCount = bit_count
-
-    Args:
-        v (int): Value to count.
-
-    Returns:
-        Number of 1 bits in the binary representation of ``v``.
-    """
-
-    if v > 0xFFFFFFFF:
-        return popCount(v >> 32) + popCount(v & 0xFFFFFFFF)
-
-    # HACKMEM 169
-    y = (v >> 1) & 0xDB6DB6DB
-    y = v - y - ((y >> 1) & 0xDB6DB6DB)
-    return (((y + (y >> 3)) & 0xC71C71C7) % 0x3F)