[dir] Selectors in input are not well supported

[rolfen]

Input

[dir="ltr"] fl {
	float:right;
}

Output

[dir="ltr"] fl {
	float:right;
}

html[dir="ltr"] [dir="ltr"] fl {
}

html[dir="rtl"] [dir="ltr"] fl {
}

There may be two issues here:

• [dir] selectors in input are a spacial case should be ignored or better handled.
• Maybe empty declarations should not be printed. As a workaround, I'm using postcss-discard-empty to filter them out.