SUSTACK - stack adjacent traces having the same key header word

sustack <stdin >stdout [Optional parameters]

Required parameters:
none

Optional parameters:
key=cdp header key word to stack on
normpow=1.0 each sample is divided by the
normpow'th number of non-zero values
stacked (normpow=0 selects no division)
verbose=0 verbose = 1 echos information

Note: The offset field is set to zero on the output traces.
Sushw can be used afterwards if this is not acceptable.

Credits:
SEP: Einar Kjartansson
CWP: Jack K. Cohen, Dave Hale

Note:
The "valxxx" subroutines are in su/lib/valpkge.c. In particular,
"valcmp" shares the annoying attribute of "strcmp" that
if (valcmp(type, val, valnew) {
...
}
will be performed when val and valnew are different.

Trace header fields accessed: ns
Trace header fields modified: nhs, tracl, offset