arm-xo-1.75: drop wljoin from olpcbasics.fth

split.fth provides it now.
diff --git a/src/app/arm-xo-1.75/olpcbasics.fth b/src/app/arm-xo-1.75/olpcbasics.fth
index 7cddbd2..40e39b8 100644
--- a/src/app/arm-xo-1.75/olpcbasics.fth
+++ b/src/app/arm-xo-1.75/olpcbasics.fth
@@ -6,7 +6,6 @@
 
 fl ../arm-xo-1.75/addrs.fth
 
-: wljoin  ( w w -- l )  d# 16 lshift or  ;
 : third  ( a b c -- a b c a )  2 pick  ;
 fl ../arm-mmp2/lcd.fth