macOS system language detection.

It appears the system language detection doesn't work on [some versions
of?] macOS.  Fixed.

Strangely, querying the Cocoa API for the system locale on a system in
US with the preferred language set to Korean produces the invalid locale
"ko-US" instead of the expected "ko-KR".  This behavior of returning the
language with a invalid region qualifier for the language appears to
happen only with languages where macOS does not have regional variants
(this issue does not seem to occur with Canadian English, en-CA, for
example.)  A fuzzy matching locale function has been added to handle
this issue.

src/ios.m

@@ -49,6 +49,12 @@ void apple_init(void)
 }
 
 
+const char *apple_locale(void)
+{
+    return ""
+}
+
+
 const char *apple_fontsPath(void)
 {
     return IOS_FONTS_PATH;