for consistency, always allow 'onelevel' as an alias for 'one' in dnstyle

doc/man/man5/slapd.access.5

@@ -91,11 +91,15 @@ or
 .B exact 
 (an alias of 
 .BR base )
-indicates the entry whose DN is equal to the pattern.
+indicates the entry whose DN is equal to the pattern;
 .B one
+(synonym of
+.BR onelevel )
 indicates all the entries immediately below the
 .BR pattern ,
-.B subtree
+.B sub
+(synonym of
+.BR subtree )
 indicates all entries in the subtree at the pattern,
 .B children
 indicates all the entries below (subordinate to) the pattern.