Write max_local to language files during sync

If your language has a bigger font, the max attribute isn't really
helpful to you as a translator, so the sync feature adds a special
max_local attribute which is accurate to the font size. This was
already documented in advance.

If used, we now also write an attribute in the root tag of strings.xml
and strings_plural.xml, that looks like max_local_for="12x12". I
decided to add this attribute after finding out the Excel macros would
be really hard to change to only show a max_local column if it is ever
used (it'd need to look ahead through the strings until it finds a
string with a max, or remove the column if no string has used it), but
it's also a convenience for translators.

desktop_version/src/LocalizationStorage.cpp

@@ -252,7 +252,7 @@ void resettext(bool final_shutdown)
     resettext_custom(final_shutdown);
 }
 
-static bool parse_max(const char* max, unsigned short* max_w, unsigned short* max_h)
+bool parse_max(const char* max, unsigned short* max_w, unsigned short* max_h)
 {
     /* Parse a max string, like "33" or "33*3", into two shorts.
      * Returns true if successful and max_w/max_h have gotten valid values, false otherwise. */