restore lazy_import of maxima in calculus.py

Author: nbruin

src/sage/calculus/calculus.py

@@ -426,7 +426,8 @@
 from types import FunctionType
 
 from sage.arith.misc import algebraic_dependency
-from sage.interfaces.maxima_lib import maxima
+from sage.misc.lazy_import import lazy_import
+lazy_import("sage.interfaces.maxima_lib","maxima")
 from sage.misc.latex import latex
 from sage.misc.parser import LookupNameMaker, Parser
 from sage.rings.cc import CC