Regression: border: 0px somestyle somecolor is transformed into border: 0

[RReverser]

Ironically, CSS refactor PR (#177) that fixed one border issue fixing one border related issue (#176) seems to have created another obscure border issue.

Now CSS that looks like

.x {
  border: 0px dashed red;
}

is minified into

.x{border:0}

This transformation is incorrect as it doesn't take into account whether other values being removed actually correspond to their defaults from the spec. In some cases this results in break of cascading behaviour when such stylesheet is combined with another:

.x {
  border-width: 1px;
}

Previously, combination of these would result in equivalent of border: 1px dashed red, but after minification border-style remains none and border doesn't appear.