Fix warnings in the extend_template_method, li_std_string, and
template_methods tests. std::string was missing a typecheck typemap.
Add extend_template_method_runme.ml, li_std_string_runme.ml, and
template_methods_runme.ml.
Add INPUT, OUTPUT and INOUT typemaps for string &
Use the INOUT typemap in the strings_test example. In the
strings_test example, takes_and_gives_std_string() was relying on the
silly fact that an argout typemap for string & was enabled by
default.
Remove the in, out, and typecheck typemaps for string &.
Closes: #1439
Update some of the OCaml examples so that they run successfully with
`make check-ocaml-examples` (important for the CI). Some of the
examples were written to depend on passed arguments.
Temporarily disable the broken std_string example.