## Import seitosh

@wittkamp @lgass @r libstfinv in Seitosh provides a new feature:

A new taper option for procedures operating in the Fourier domain is implemenetd in libstfinv. This can be used to remove unwanted acausal or coda components of the impulse response of the source time function correction filter. See usage information provided by libstfinv:

```
A time domain taper can be applied to the impulse response of the correction
filter by using option irtap. Four time values are given in units of seconds:
t1, t2, t3, and t4. They must be in increasing order and (t4-t1) must be
smaller than the total duration of the time series used to represent signals
internally. Times value are allowed to be negative. Time series are understood
to be periodic (due to discrete Fourier transformation). Prior to application
of the correction filter to the time series passed to the algorithm, the
correction filter is transformed to the time domain, tapered, and then
transformed to the Fourier domain again. The values of the taper are:
0 if t < t1
0.5-0.5*cos(pi*(t-t1)/(t2-t1)) if t1 <= t <= t2
1 if t2 < t < t3
0.5+0.5*cos(pi*(t-t3)/(t3-t4)) if t3 <= t <= t4
0 if t > t4
```

Test-cases are set up for soutifu and are described in the accompanying README.soutifu.

A vendor update has taken place in thof/IFOS2D see issue 5 there. The code in contrib compiles and installs well. The integration into IFOS2D still is to be tested.