c++/1687: Extreme compile time regression from 2.95.2

[Wolfgang Bangerth]

> Wolfgang, you were the last to re-confirm the PR, do you still
> see it?

I see long compile times for the C front-end, but it compiles 
instantaneously with the C++ front end. Don't know whether that's just a 
problem on my side or true -- can you check this (sorry, don't have time 
right now...).

W.

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Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/