Comment out OpenMP sections

The OpenMP directives in this source file result in an internal
compiler error on SL6. Since LALSimulation may be built with
OpenMP now, we may inherit the OpenMP compiler flags.
Use I0(snr^2 |autocorrelation|) for timing likelihood
Factor out signal model
Whitespace
Faster, and less alias-y, method of computing autocorrelation
Implement new autocorrelation likelihood in Gaussian quadrature functions
Track API change in LALSimulation
Suppress underflow errors
Whitespace