devel/linux-c7-systemd-libs: Install libudev.so library.

This reverts commit 516aa73ebc6276c688b7c7bcc815658ece81b583
"Don't install libudev.so. The linux flash player plugin tries to use it"

We do not have Linux Flashplayer in the tree anymore. Also the libudev library
seems to be working fine.

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