Location of APR/APU docs changed

You may have noticed that location of APR/APU documentation changed on
APR website (it is now version specific). Although the old links should
work, they are actually referring to version 0.9, which may or may not
be what APREQ docs should point to (current APREQ were most likely built
against 1.2).

Changing APREQ build system to link to APR/APU docs with a specific
version number would be the correct thing to do. All this FYI, of
course.

-- 
Bojan