busybox

The last patch broke:
sed -i "/^boo/a fred" ipsec.conf

Which works in gnu sed.  (And is _supposed_ to strip all the whitespace before
"fred".)

It also broke:
sed -i -e "/^boo/a \\" -e "   fred" ipsec.conf

I.E. there can legally be spaces between the a and the backslash at the end of
the line.

And strangely enough, gnu sed accepts the following syntax as well:
sed -i "/^boo/a \\  fred" ipsec.conf

Which is a way of having the significant whitespace at the start of the line,
all on one line.  (But notice that the whitespace BEFORE the slash is still
stripped, as is the slash itself.  And notice that the naieve placement of
"\n" there doesn't work, it puts an n at the start of the appended line.  The
double slashing is for shell escapes because you could escape the quote, you
see.  It's turned into a single backslash.  But \n there is _not_ turned into
a newline by the shell.  So there.)

This makes all three syntaxes work in my tests.  I should probably start
writing better documentation at some point.  I posted my current sedtests.py
file to the list, which needs a lot more tests added as well...