Sed 3.0

This version of sed passes the new test-suite donated by
Jason Molenda.

Overall performance has been improved in the following sense: Sed 3.0
is often slightly slower than sed 2.05.  On a few scripts, though, sed
2.05 was so slow as to be nearly useless or to use up unreasonable
amounts of memory.  These problems have been fixed and in such cases,
sed 3.0 should have acceptable performance.
