Backport of 46603.

This adds support for symbol versioning which is needed on
CentOs/RedHat 7 to fix #20134.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@46681 3c298f89-4303-0410-b956-a3cf2f4a3e73