Bug 795039 - Crash on startup using Technicolor Style sheet in report

The mingw-w64 toolchain bizarrely substitutes scm_to_locale_string()
for scm_to_utf8_string(). This results in latin1 (yeah, "locale" is
a lie) instead of utf8 which causes an assertion in
g_utf8_collate_key().

Perhaps equally bizarre, the compiler doesn't make the substitution
with scm_to_utf8_stringn(), so use that instead.

libgnucash/core-utils/gnc-guile-utils.c

@@ -43,7 +43,7 @@ gchar *gnc_scm_to_utf8_string(SCM scm_string)
         gchar* s;
         char * str;
 
-        str = scm_to_utf8_string(scm_string);
+        str = scm_to_utf8_stringn(scm_string, NULL);
         s = g_strdup(str);
         free (str);
         return s;