X11: Use libX11 UTF-8 support when available.

This saves quite a bit of library size. STR #3107


git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10237 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Xutf8.h

@@ -142,6 +142,9 @@ long
 XKeysymToUcs(
 	KeySym 	keysym);
 
+#ifdef X_HAVE_UTF8_STRING
+#define XUtf8LookupString Xutf8LookupString
+#else
 int
 XUtf8LookupString(
     XIC                 ic,
@@ -150,6 +153,7 @@ XUtf8LookupString(
     int                 bytes_buffer,
     KeySym*             keysym,
     Status*             status_return);
+#endif
 
 unsigned short
 XUtf8IsNonSpacing(

src/xutf8/utf8Input.c

@@ -407,6 +407,7 @@ XConvertEucToUtf8(const char*	locale,
   return len;
 }
 
+#ifndef X_HAVE_UTF8_STRING
 int
 XUtf8LookupString(XIC                 ic,
 		  XKeyPressedEvent*   event,
@@ -447,6 +448,7 @@ XUtf8LookupString(XIC                 ic,
   }
   return len;
 }
+#endif /* X11 has utf-8 */
 
 #endif /* X11 only */