Otherwise you might wind up with things like...
my $path1 = undef;
my $path2 = 'foo';
my $path = $path1 . '/' . $path2;
creating '/foo'. Or this...
my $path1 = 'foo/';
my $path2 = 'bar';
my $path = $path1 . '/' . $path2;
creating 'foo//bar'.
Could have used File::Spec, but I'm shying away from it due to SVN
1.7's pickiness about paths. Felt it would be better to have our own
we can control completely.
[ew: commit title]
Signed-off-by: Eric Wong <normalperson@yhbt.net>