Log Message:
Fix qpdfview.
Don't use DESTDIR in qpdfview.pri since this makes qpdfview look for
it's plugins under ${DESTDIR}${PREFIX} when it should look under
${PREFIX} .
Use INSTALL_ROOT to install into DESTDIR.
Use environment variables instead of the substitution framework to set
PREFIX and PKGMANDIR.
Bump PKGREVISION.