bug#25397: guile-2.2 regression in utf8 support in scm_puts scm_lfwrite scm_c_put_string

[Linas Vepstas <linasvepstas@gmail.com>]

There appears to be a regression in guile-2.2 with utf8 handling
in the scm_puts() scm_lfwrite() and scm_c_put_string() functions.

In guile-2.0, one could give these utf8-encoded strings, and these
would display just fine.  In 2.2 they get mangled.

The source of the mangling seems to be an assumption that these
three are being given latin1 strings, which they then attempt to
convert to utf8, thus wrecking the encoding.  See, e.g. libguile/ports.c
line 3526

Presumably this change was intentional, but I don't understand
why; guile-2.0 seems utf-8 clean, correctly handling utf-8 in
essentially all cases.  Why would one want to go back to the
bad old days of latin1 and iso-8859-1 for guile 2.2?

I could submit a patch for this, but would it be wanted?

Test case is straight-forward:

printf("duuude port-encoding is=%s\n",
   scm_to_utf8_string(scm_port_encoding(scm_current_output_port ())));
scm_puts ("係 拉 丁 字 母", scm_current_output_port ());

which works in guile-2.0 but is garbled in 2.2