Do not use bitcoin::blockdata

Do not use bitcoin::blockdata

The `rust-bitcoin` project is working towards making the public API
separate from the directory structure; eventually the
`bitcoin::blockdata` will go away, to make maintenance easier here stop
using the `blockdata` module.

Do not run the formatter, so as to make review easier. This patch was
created mechanically using:

search-and-replace bitcoin::blockdata bitcoin

and having defined

```bash
search-and-replace () {
        if (($# != 2))
        then
                echo "Usage: $0 <this> <that>"
                return
        fi
        local this="$1"
        local that="$2"
        for file in $(git grep -l "$this")
        do
                perl -pi -e "s/$this/$that/g" "$file"
        done
}
```