The compiler has better error messages for methods called without a
pointer receiver when one is expected. This change is similar to
CL 229801, but for method calls.
Also, added better error messages for functions called with the wrong
capitalization. I left the third TODO in this switch statement almost
as-is because I'm not sure that the extra complexity is worth it -
I adjusted the error to look like the one the compiler reports.
Run-TryBot: Rebecca Stambler <firstname.lastname@example.org>
TryBot-Result: Gobot Gobot <email@example.com>
Reviewed-by: Robert Griesemer <firstname.lastname@example.org>