Fix C++ compile failures in headers.

Avoid using "typeid" as a parameter name in header files, since that
is a C++ keyword.  These cases were introduced recently, in 04fe805a1
and 586b98fdf.

Since I'm an incurable neatnik, also rename these parameters in the
underlying function definitions.  That's not really necessary per
project rules, but I don't like function declarations that don't
quite agree with the underlying definitions.

Per src/tools/pginclude/cpluspluscheck.
