Do not recompile when changes are confined to comments and non-significant white space

Motivation

Documentation and other text annotations inevitably get out of sync with code, but in the interest of minimizing the time cost of keeping these in sync it would be beneficial to make the compiler smart enough to recognize when edits are confined to the parts intended only for human consumption.

Proposal

Currently if you make an edit, try and fail to compile, and then revert the edit, the compiler recognizes that the source corresponds to the previously success and does not do the build. This change would take this further, and omit compiles when there is no change to the source once stripped of its comments.