Multiline properties should not be parsed as key / value

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Eg. the following @font-face declaration fails

b.css({
  '@font-face': b(`
    font-family: 'Titillium Web';
    font-weight: 200;
    font-style: normal;
    src: url('/fonts/Titillium-Web-200.eot');
    src: url('/fonts/Titillium-Web-200.eot?#iefix') format('embedded-opentype'),local('Titillium WebThin'),local('Titillium-Web-200'),url('/fonts/Titillium-Web-200.woff2') format('woff2'),url('/fonts/Titillium-Web-200.woff') format('woff'),url('/fonts/Titillium-Web-200.ttf') format('truetype'),url('/fonts/Titillium-Web-200.svg#TitilliumWeb') format('svg');
  `)
})