No include guard indent

Hi Ben,

Here is an update of the tool mainly to apply "#include guard" strategy to code.
 I have not created an option as it seems that this update has no impact on tests.
 But if you prefer I add an option, don't hesitate to ask me.

Specific actions were taken for preprocessor directives.
 It is now extended to all code:
 - code inside the "#include guard" is not indented
 - optimization of "ifdef_over_whole_file" to be able to call it several times
 
+ Update of the comment of some options to clarify their actions

I merged your last updates in this branch but it wa not really intentional (test of a command that didn't do what I expected to) => I have not tested this merge.

This replace pull request #67 that I closed (code not pushed correctly from my local repository and the github repository).
 
Ronan