perl 1.0 patch 12: scripts made by a2p doen't handle leading white space right on...

perl 1.0 patch 12: scripts made by a2p doen't handle leading white space right on input

Awk ignores leading whitespace on split.  Perl by default does not.
The a2p translator couldn't handle this.  The fix is partly to a2p
and partly to perl.  Perl now has a way to specify to split to
ignore leading white space as awk does.  A2p now takes advantage of
that.

I also threw in an optimization that let's runtime patterns
compile just once if they are known to be constant, so that
split(' ') doesn't compile the pattern every time.