"Unknown compiler version - please [...]" text content should be improved

[Daniel Krügler <daniel.kruegler@…>]

The compiler specific .hpp files in boost/config/ all have a fallback text that is shown as message (or error message, depending on BOOST_ASSERT_CONFIG being set or not) with the following text:

"Unknown compiler version - please run the configure tests and report the results"

We met this message recently after an update of the VS 2017 compiler from 15.2 to 15.3 (which decided to change _MSC_VER from 1910 to 1911), see ticket:13167 and given Microsofts new compiler version policy it is expected that this message will occur quite often in the future. But the request of this issue is different from ticket:13167: Please extend that text output to make clear who is complaining here, for example

"boost compiler configuration: Unknown compiler version - please run the configure tests and report the results"

I'm strongly encouraging to provide something like this text enhancement, because the text appears in between a lot of other compiler messages, so the unaware reader of the full preprocessor output cannot remotely guess at this point, where this request comes from. I'm willing to provide a concrete pull request once there is consensus about the concrete text change. Personally I'm open in regard to the details, but my suggestion would be to provide additional context information. I would guess that the minimum text change would simply be along the lines of:

"Boost: Unknown compiler version - please run the configure tests and report the results"

[John Maddock]

This has since been changed.