Correlate NoMessageBoxes with SuppressMessageBoxes in documentation/comments

[jpluimers]

Edit

The global Boolean variable SuppressMessageBoxes already suppresses the effect of a missing NoMessageBoxes define, but it is not obvious these are correlated.

Adopt documentation/comments to make their relation more obvious.

Time permitting, I will submit a pull-request.

Original title

Have NoMessageBoxes depend on a global boolean

Original

Sometimes I want the NoMessageBoxes to depend on run-time circumstances, for instance:

• force NoMessageBoxes when running as a standalone process
• disable NoMessageBoxes when running under the debugger

For that, it would be nice if NoMessageBoxes was implemented through a global variable.

Time permitting, I will submit a pull-request.