[Bug c/84890] Overly verbose notes for missing headers

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84890

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I have very little sympathy for anybody who thinks that an automated message
from a compiler is "kind of personal", but how about instead of asking a
question or equivocating with "you may want to ..." just say what the required
header is:

   #include <foo.h> to define std::foo