Add platform-independent Unicode setup function.

Similarly to the one I just added for FontSpec: in a cross-platform
main source file, you don't really want to mess about with
per-platform ifdefs just to initialise a 'struct unicode_data' from a
Conf. But until now, you had to, because init_ucs had a different
prototype on Windows and Unix.

I plan to use this in future test programs. But an immediate positive
effect is that it removes the only platform-dependent call from
fuzzterm.c. So now that could be built on Windows too, given only an
appropriate cmake stanza. (Not that I have much idea if it's useful to
fuzz the terminal separately on multiple platforms, but it's nice to
know that it's possible if anyone does need to.)

putty.h

@@ -286,6 +286,11 @@ struct unicode_data {
 #define LGTYP_PACKETS 3                /* logmode: SSH data packets */
 #define LGTYP_SSHRAW 4                 /* logmode: SSH raw data */
 
+/* Platform-generic function to set up a struct unicode_data. This is
+ * only likely to be useful to test programs; real clients will want
+ * to use the more flexible per-platform setup functions. */
+void init_ucs_generic(Conf *conf, struct unicode_data *ucsdata);
+
 /*
  * Enumeration of 'special commands' that can be sent during a
  * session, separately from the byte stream of ordinary session data.

test/fuzzterm.c

@@ -21,9 +21,7 @@ int main(int argc, char **argv)
 
     conf = conf_new();
     do_defaults(NULL, conf);
-    init_ucs(&ucsdata, conf_get_str(conf, CONF_line_codepage),
-             conf_get_bool(conf, CONF_utf8_override),
-             CS_NONE, conf_get_int(conf, CONF_vtmode));
+    init_ucs_generic(conf, &ucsdata);
 
     term = term_init(conf, &ucsdata, &termwin);
     term_size(term, 24, 80, 10000);

unix/unicode.c

@@ -243,6 +243,13 @@ bool init_ucs(struct unicode_data *ucsdata, char *linecharset,
     return ret;
 }
 
+void init_ucs_generic(Conf *conf, struct unicode_data *ucsdata)
+{
+    init_ucs(ucsdata, conf_get_str(conf, CONF_line_codepage),
+             conf_get_bool(conf, CONF_utf8_override),
+             CS_NONE, conf_get_int(conf, CONF_vtmode));
+}
+
 const char *cp_name(int codepage)
 {
     if (codepage == CS_NONE)

windows/unicode.c

@@ -689,6 +689,11 @@ void init_ucs(Conf *conf, struct unicode_data *ucsdata)
     }
 }
 
+void init_ucs_generic(Conf *conf, struct unicode_data *ucsdata)
+{
+    init_ucs(conf, ucsdata);
+}
+
 static void link_font(WCHAR *line_tbl, WCHAR *font_tbl, WCHAR attr)
 {
     int font_index, line_index, i;