Changes to fe_simulation and awgtpman to allow arbitrary excitations on simulated front ends.

'-a' command line option is added to fe_simulation_streams to get testpoint data from awgtpman instead of command line

'-g' and '-m' options added to awgtpman.

'-g' uses gps time kernel module to get the time, instead of waiting for the time from iop model.

'-m' sets a shared memory prefix, so that awgtpman can use POSIX shared memory instead of mbufs

Purpose is to allow portable testing of DTT.

awgtpman passes basic tests on large test stand.