The patch is going to replace the implementation from r323625.
The original implementation adds a section with AT attribute into the same load segment
as a previous section if that segment does not contain a section with a customized LMA.
After that, this attribute affects not only this and following sections, as required by specs,
but also previous sections in that segment.
I believe that a better way is to just start a new segment if we encounter a section
with AT attribute, with the only exception for the very first section, because we have added
header sections in the first load segment. It looks like GNU ld does the same.