The use of the SP_PATH variable under Windows is discouraged,
since Windows applications can find out for themselves where they were
started from.
SP_PATH is only used if the directory where sprt310.dll
is loaded from does not contain sp-3.10.1 (a directory),
sprt.sav, or spre.sav.
If SP_PATH is used, SICStus expects it
to be set such that %SP_PATH%\bin contains sprt.sav or
spre.sav. See Runtime Systems on Target Machines.