Fine-grained control over function name replacements

[ZibingZhang]

Description

In #152, we discovered a case that when factorial is replaced by !, the behavior is not desirable.

In particular, when defining a recursive function factorial with style=ALGORITHMIC, e.g.

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)

we should not replace factorial with ! in the recursive case, because that is also the name of the function.

Expected behavior

factorial should stay as factorial.