[RFA v3 00/13] various frame filter fixes and cleanups

[Tom Tromey <tom at tromey dot com>]

This is version 3 of a series that I last sent last August:

https://sourceware.org/ml/gdb-patches/2017-08/msg00277.html

Most of the patches were already approved, though of course it doesn't
hurt to check again.  At least patch #1 needed some reworking in order
to be rebased on top of the changes that have been made since August.

This version addresses most of the review comments from version 2.
Also, in response to Pedro's feedback about the choice of "elide" as
the option name, I've changed the new command to be "bt hide".  I
think this should be unambiguous.

I have not addressed Phil's comments:

https://sourceware.org/ml/gdb-patches/2017-08/msg00360.html
https://sourceware.org/ml/gdb-patches/2017-08/msg00359.html

One reason is that I agree with Pedro's comment here:

https://sourceware.org/ml/gdb-patches/2017-08/msg00297.html

Another reason is that I think that the two ideas can live together,
if necessary: I'd still appreciate a way to hide frames from the
command line, overriding whatever individual frame filters think is
appropriate.  Similarly, adding this feature to frame filters would
not impact this series -- it can always still be done after this.

Regression tested by the buildbot.

Tom