c++/6839: ICE on illegal explicit member function instantiation syntax

[Wolfgang Bangerth]

A minimal example for this ICE in all gcc versions is of course
-------------------------------
template <typename T> class X {
    void f(){};
};
template void X<int>::f;
-------------------------------

Note the missing parentheses in the explicit instantiation.
W.

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