[CSS21] Clarify auto margins on absolutely-positioned replaced elements

Section 10.6.5 says

   "The used value of 'height' is determined as for inline replaced elements."

later on it says

   "If at this point both 'margin-top' and 'margin-bottom' are still 'auto',
   solve the equation under the extra constraint that the two margins must
   get equal values."

I assume this means the sentence from 10.6.2 (inline replaced elements)

   "If 'margin-top', or 'margin-bottom' are 'auto', their used value is 0."

is not supposed to be applied. I think this needs to be clarified.

~fantasai