src: allow setting a default language in the CLI tool.

The syntax of --weight stays the same with the addition that the
language '*' means setting the default weight.

For instance, if you are sure that your input is either French or
English, you could run:

> uchardet -l -w 'fr:1,en:1,*:0'

(setting same weight to French and English, and everything else to 0)

src/tools/uchardet.cpp

@@ -190,6 +190,9 @@ int main(int argc, char ** argv)
                         return 1;
                     }
                     *comma = '\0';
+                    if (strcmp (lang_weight, "*") == 0)
+                        uchardet_set_default_weight(handle, strtof (comma + 1, NULL));
+                    else
                         uchardet_weigh_language(handle, lang_weight, strtof (comma + 1, NULL));
                 }
                 while ((lang_weight = strtok_r (NULL, ",", &saveptr)));