tools: fix regression in doctool

101dd1ed introduced a regression in the doctool. This commit reverts
the changes that were made to the function signature of the various
doctool functions while maintaining support for passing in specific
node versions.

Refs: https://github.com/nodejs/node/commit/101dd1e

PR-URL: https://github.com/nodejs/node/pull/6680


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Robert Lindstaedt <robert.lindstaedt@gmail.com>