compiler.tree.propagation.transforms: fix redundant-bitand?.

compiler.tree.propagation.transforms: fix redundant-bitand?.

When removing a redundant bitand (for example, in ``W*`` which does ``64
on-bits bitand``) make sure that we leave the ``>bignum`` to convert the
input integer to a bignum since the output type propagation assumes that
to be the case and we compiled the following code wrong.

    : mult ( a b -- x ) [ 32 bits ] bi@ W* ;

Before:

    \ mult optimized.
    [
        >R 4294967295 >R integer>fixnum R> fixnum-bitand
        R> 4294967295 >R integer>fixnum R> fixnum-bitand fixnum*
    ]

After:

    \ mult optimized.
    [
        >R 4294967295 >R integer>fixnum R> fixnum-bitand
        R> 4294967295 >R integer>fixnum R> fixnum-bitand fixnum*
        >bignum
    ]