thunderbird-patch-inline: avoid bashism

thunderbird-patch-inline: avoid bashism

The use of "echo -e" is not portable and not specified by POSIX.  dash
does not support any options except "-n", and so this script will not
work on operating systems which use that as /bin/sh.

Fortunately, the solution is easy: switch to printf(1), which is
specified by POSIX and allows the escape sequences we want to use.  This
will allow the script to work with any POSIX shell.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>