VOMS Clients v. 2.0.12

This release provides a new packaging of the native clients that can coexist with the new Java clients and some bug fixes.

VOMS-495 : Make voms-clients3 packages installable together with voms-clients
VOMS-381 : voms-proxy-init crashes when run as root and host certificate is not present
VOMS-516 : Stack smashing in voms-proxy-init