classes.struct: fix some bugs in binary-zero?, add unit tests

basis/classes/struct/struct-tests.factor

@@ -9,6 +9,7 @@ system tools.test parser lexer eval layouts generic.single classes
 vocabs ;
 FROM: math => float ;
 FROM: specialized-arrays.private => specialized-array-vocab ;
+FROM: classes.struct.private => binary-zero? ;
 QUALIFIED-WITH: alien.c-types c
 SPECIALIZED-ARRAY: char
 SPECIALIZED-ARRAY: int
@@ -474,4 +475,3 @@ CONSULT: struct-test-delegate struct-test-delegator del>> ;
         7 >>a
         8 >>b
 ] unit-test
-

basis/classes/struct/struct.factor

@@ -11,6 +11,7 @@ namespaces assocs vocabs.parser math.functions
 classes.struct.bit-accessors bit-arrays
 stack-checker.dependencies system layouts ;
 FROM: delegate.private => group-words slot-group-words ;
+FROM: math => float ;
 QUALIFIED: math
 IN: classes.struct