This behaves like the function `lisp-indent-function', except that:
i) it checks for a non-nil value of the property `scheme-indent-function'
-\(or the deprecated `scheme-indent-hook'), rather than `lisp-indent-function.'
+\(or the deprecated `scheme-indent-hook'), rather than `lisp-indent-function'.
ii) if that property specifes a function, it is called with three
arguments (not two), the third argument being the default (i.e., current)