Some CSS doesn't get parsed right

[markoheijnen]

I was testing CSS minifies out and for CSSqueeze the following parts break the CSS. I used bootstrap 4.0.0 alpha 2 to testing things out.

background-image: url("data:image/svg+xml;base64,PHN2ZyB4b...");
becomes
background-image : url(data;

filter: "progid:DXImageTransform.Microsoft.gradient(enabled = false)";
becomes
filter : "progid;