But `s/' is still invalid, use `s//' instead.
If first regex is invalid, regex pointer is now set to NULL so that repeating
the search correctly reports "No previous pattern".
where IC is of the form [::] , [..], or [==], would incorrectly
report an error.
Fixed input mode bug: a literal ^J(i.e., ^V^J) would discard text
following it. Now, a literal ^J is treated as an ordinary ^J - i.e, it
splits a line in two.
