Fixed non-ASCII characters in Doxygen comment so they are UTF-8 encoded.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10756 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/fl_utf8.cxx

@@ -358,8 +358,8 @@ int fl_latin12utf(const unsigned char *str, int len, char *buf)
   returns true if the character is non-spacing.
   
   Non-spacing characters in Unicode are typically combining marks like
-  tilde (~), diaresis (¨), or other marks that are added to a base
-  character, for instance 'a' (base character) + '¨' (combining mark) = 'ä'
+  tilde (~), diaeresis (¨), or other marks that are added to a base
+  character, for instance 'a' (base character) + '¨' (combining mark) = 'ä'
   (German Umlaut).
 
   http://unicode.org/glossary/#base_character