Add support for [attr|="value"] selector (prefix selector)

Add support for [attr|="value"] selector (prefix selector)

http://www.w3.org/TR/css3-selectors/#attribute-selectors
http://www.w3.org/TR/CSS2/selector.html#attribute-selectors
http://api.jquery.com/attribute-contains-prefix-selector/

  Description: Selects elements that have the specified attribute with
  a value either equal to a given string or starting with that string
  followed by a hyphen (-).

  This selector was introduced into the CSS specification to handle
  language attributes.

Note that this selector is primarily intended to allow language
subcode matches (e.g., the `hreflang` attribute on the <a> element in
HTML; for `lang` or `xml:lang` attribute there is `:lang`
pseudo-class selector).