bootstrap: adopt autoconf echo normalization code.

bootstrap: adopt autoconf echo normalization code.

Dash shipped with Ubutu-11.10 as /bin/sh, among others, still
has a crippled echo builtin that mis-handles backslashes.
* build-aux/options-parser (bs_echo): Adopt the autoconf echo
normalization code to find a suitable replacement for buggy echo
commands.
Adjust all uses of echo to $bs_echo.
* build-aux/extract-trace (func_extract_trace, func_main):
Likewise.
* bootstrap: To retain some execution speed on platforms with
buggy builtin echo, replace most occurrences of `echo' with
`$bs_echo' - except where its arguments will obviously never
contain backslashes or be overly long.
Reported by Reuben Thomas.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>