tracing on commands with possibly-escaped newlines.
* doc/autoconf.texi (Writing testsuite.at): Delete documentation of the
discontinued behavior and its implications.
* tests/autotest.at (BS-newline in command, ^BS-newline in command)
(BSx641-newline in command, BS-BS-newline in command)
(BSx640-newline in command, Newline-CODE-BS-newline in command)
(Single-quote-BS-newline in command)
(Single-quote-newline-BS-newline in command): New tests.
* tests/.cvsignore: Add wrapper.in.
* man/Makefile.am (autoconf.1): Regenerate when `autoconf.as' changes.
* lib/autotest/general.m4 [--trace] (AT_INIT): Do not `set -v'.
* tests/autotest.at: New file.
* tests/suite.at: Include it.
* tests/Makefile.am: Distribute it.
* lib/autotest/general.m4 [--trace] (_AT_CHECK): Do not enable
shell tracing on a command that could contain multiple lines.
* doc/autoconf.text: Document that fact and its implications.
* lib/m4sugar/m4sh.m4 (AS_ESCAPE_FOR_EXPAND): New macro.
* tests/autotest.at (Multiline backquote command substitution,
Multiline parameter expansion, Literal multiline command,
Multiline parenthetical command substitution): Remove XFAIL.