Get the type of the value that a variable is currently holding. This value can be
long scriba_GetVariableType(pSbProgram pProgram,
The argument lSerial should be the serial number of
the variable as returned by scriba_LookupVariableByName().
If there is no variable for the specified serian mumber (lSerial is not positive or larger than the number of variables) the function returns SBT_UNDEF.