My fix for 61214 to clear DECL_EXTERNAL on inline virtual functions when
devirtualizing caused 62224: devirtualizing and inlining such a function
in the testcase causes an additional external reference, which in the
submitter's library is to a hidden symbol.
I think this is what we want for 5.0, but for 4.9.2 it's probably better
to avoid breaking things that worked with 4.9.1.
So that means we want to fix 61214 a different way. Does it make sense
to check DECL_EXTERNAL in can_refer_decl_in_current_unit_p in 4.9 the
way we already do in 5.0?
Tested x86_64-pc-linux-gnu. OK for 4.9.2?
