bug#6991: Please keep bytecode out of *Backtrace* buffers

[npostavs]

npostavs@users.sourceforge.net writes:

> I propose adding a new flag print_escape_control_characters instead (see
> patch #3 in the series).  I also implemented hiding the byte code
> functions with text properties in #4.  It's not quite satisfactory
> though, because it doesn't cover byte code functions values that are
> arguments, only byte code being called.  I think printing needs to be
> made more flexible in order to cleanly catch all byte code values.
> Patch #5 replaces NUL bytes with "\0" in X selections (I guess it covers
> w32 as well? Haven't checked yet).

Updated the patchset to use cl-prin1, now it applies to function values
in arguments as well.  This one actually doesn't include the byte code
text at all (path of least resistance: cl-print-object wasn't already
omitting bytecode and I haven't bothered adding it).

v2-0001-Operate-on-frame-list-instead-of-printed-backtrac.patch
Description: patch

v2-0002-Improve-ert-backtrace-recording.patch
Description: patch

v2-0003-Escape-control-characters-in-backtraces-Bug-6991.patch
Description: patch

v2-0004-Hide-byte-code-in-backtraces-Bug-6991.patch
Description: patch

v2-0005-Escape-NUL-bytes-in-X-selections-Bug-6991.patch
Description: patch

v2-0006-Don-t-redundantly-cl-print-arglist-in-function-do.patch
Description: patch