Add support to detect the expansion of $LIB and $PLATFORM
When loading VDPAU modules we rely on $PLATFORM, trying to support all its known possible expansions.
However there is always the possibility that we are currently missing some of them or that new ones will be added in the future.
For this reason we try to detect the expansion of $PLATFORM, and $LIB, and print its value in the report. In this way it will be easier to notice unusual and/or new expansions.
Its still missing some automatic and manual tests, and double checking what I added so far.
I moved the first commit to !296 (merged) because it was not entirely related to this feature.
/cc @smcv
Edited by Ludovico de Nittis