adding a runtime dependency into KDELIBS

[Alex Fiestas]

We're in the process of merging a review which will partly fix the sad 
situation of MTP/MPI/iPod devices in libsolid, the review I'm talking 
about is:

https://git.reviewboard.kde.org/r/103028/

This as far as I know was (is) working with the linux-deprecated HAL 
backend, so is something we urge to fix.

This patch adds support for media-player-info which is basically what 
replaces some features HAL has in the new u* stuff.

So, Can I give the ship it for this patch? can we add an optional 
runtime dependency to kdelibs 4.7.x ?

Thanks.