Update overlinking URL in guide

The Mandriva wiki is just being archived now, so point to the active
OpenMandriva article instead.
Ensure usage of serial test driver in automake

Automake has a nice parallel test driver available since 1.12 which
became the default in 1.13. Unfortunately, it breaks the pkg-config
testsuite, so we need to ensure the serial test driver is used. On 1.12,
we can specify the option 'serial-tests', but this doesn't exist on
1.11. Kludge around this by detecting if the automake version is less
than 1.12 and leaving the option out in that case.
Strip system library directories reliably

This loop was changed from a while loop to a for loop in commit
9bf6277b, but the iterator is now advanced twice each time round the
loop.
Add --validate option to check .pc syntax without dependencies

Provide developers a way to check their .pc files prior to release. This
works the same as --exists except that package dependencies are not
processed. That allows the .pc file to be checked in complete isolation
of others.

Freedesktop #7000 (https://bugs.freedesktop.org/show_bug.cgi?id=7000)