Make newline in RHS of lib/configure sed substition more portable

[Tuncer Ayaz]

Commit http://github.com/erlang/otp/commit/1b78e8
seems to have introduced a non-portable RHS parameter
to a sed substitution string for expanding lib/configure's
template file.

The escaped newline character in the substitution string
does not work as expected.
On a Linux machine it inserts an additional blank line
and on OSX it only inserts a leading 'n' which gives you
a broken lib/configure script.

I've successfully tested the fix on Linux and OSX.

git fetch git://github.com/tuncer/otp.git otp_build_sed_newline