Use `#encoding: US-ASCII` magic comment for binary string literals with ruby 2.0

Using this regex, `\\[xu]?\d\d?\d?\d?` from @Fryguy, I was able to find the attached places with binary string literals.  In all cases, it's very possible that other binary string literals would be added in the future, so I chose to add the `# encoding: US-ASCII` magic comment so any additional literals would NOT need to use String#force_encoding("ASCII-8BIT") or String#b.

Note, many of these literals were the NULL character, which I don't believe would have issues as UTF-8 but to be sure, using US-ASCII is a better option for these files since it's more likely they'll be using binary strings literals than actual UTF-8 strings.