split -e currently discards input prior to the first appearance of the
given expression.  This seems to be undesirable behavior, as split
should preserve all input data (unless -x is given, which is
unconnected to this issue).  The cause is the output Biobuf lacking an
initial file association prior to the first time the regexp test is
passed.  This patch moves the match array declaration and initial call
to matchfile to prior to entering the output loop.  Tested by
mycroftiv and the initial bugfinder.  No manpage change necessary, I
believe preserving all input data is the intended behavior of split.