* config/general.m4sh (Xsed): Set a default when not used from

* config/general.m4sh (Xsed): Set a default when not used from
ltmain.in.
(ECHO): Audit for (and correct!) uses of $ECHO with more than one
argument, which breaks when ECHO='printf %sn', and with possible
`-' as first character of the argument, which breaks `print -r'
and some implementations of `echo'.
* config/ltmain.in, tests/defs.in, libtoolize.in (ECHO): Ditto.
Reported by Albert Chin-A-Young <china@thewrittenword.com>