Don't gratuitously pipe thru a cat(1) if NODOCCOMPRESS.
Only create _stamp.extra when necessary.
Get rid of SOELIMPP and OBJS.
Use Groff version of soelim(1); we need its -I option
for the following to work.
Don't needlessly chdir to SRCDIR. Only a few documents
need CD_HACK, and those that need it either use refer(1)
or .PSPIC macro which internally uses the .psbb call.
