Summary:
The performance-unnecessary-value-param check mangled inherited
constructors, as the constructors' parameters do not have useful source
locations. Fix this by ignoring implicit functions.
Fixes PR31684.
Reviewers: flx, alexfh, aaron.ballman
Subscribers: madsravn, JDevlieghere, cfe-commits
Differential Revision: https://reviews.llvm.org/D29018
llvm-svn: 292786