Reorganize imports in demo/ (no star imports)

demo/manydigits.py

@@ -8,7 +8,8 @@ Run with:
     python manydigits.py
 
 """
-from mpmath import *
+from mpmath import (mp, sin, tan, cos, sqrt, e, pi, exp, atanh, mpf, tanh,
+                    zeta, catalan, findroot, quadts, atan, asin, asinh)
 from mpmath.libmp import to_fixed, bin_to_radix
 
 dps = 100

demo/taylor.py

@@ -6,7 +6,7 @@ This module can be run interactively with
     python taylor.py
 
 """
-from mpmath import *
+from mpmath import mpi, exp, factorial, mpf
 
 def taylor(x, n):
     print("-"*75)