Attached is a first shot for OMP_DISPLAY_ENV. One could think about how 
to handle GOMP_CPU_AFFINITY and OMP_WAIT_POLICY. I currently print an 
empty list for affinity (although using GOMP_CPU_AFFINITY='' leads to a 
warning that the list is empty) and for OMP_WAIT_POLICY, an unset 
variable is handled as something between ACTIVE and PASSIVE; the patch 
prints PASSIVE in that case.

Build and regtested on x86-64-gnu-linux.
OK for the gomp-4_0-branch - after is has been created?

Tobias