C++ template completion support v3

[Keith Seitz]

I would like to resurrect this patch series (after a very long hiatus).

There are minimal changes to the original series, last posted here:

https://sourceware.org/pipermail/gdb-patches/2020-April/167780.html

During that last series, Tom (Tromey) gave it the LGTM, but there was
a request to add unittests for strncmp_iw_with_mode. This new series
accommodates that request.

The second patch from the original submission ("Remove hard-coded
line number from templates.exp") is no longer necessary,
having been fixed by Andrew Burgess in November. 

I have tested this on x86_64 Fedora 34 w/system GCC using
{unix,native-gdbserver,native-extended-gdbserver}/-m{32,64}.

I apologize that it has taken so long to get back to this.

Keith
--
gdb/NEWS                                    |   6 +-
 gdb/cp-support.c                            |  82 +++-
 gdb/cp-support.h                            |   7 +
 gdb/doc/gdb.texinfo                         |  46 ++
 gdb/linespec.c                              |  77 ----
 gdb/linespec.h                              |   7 -
 gdb/testsuite/gdb.cp/templates.cc           |  47 ++
 gdb/testsuite/gdb.cp/templates.exp          |  67 +++
 gdb/testsuite/gdb.linespec/cpcompletion.exp | 437 ++++++++++++++++++-
 gdb/testsuite/gdb.linespec/cpls-ops.exp     |  53 +--
 gdb/testsuite/gdb.linespec/cpls.cc          | 110 ++++-
 gdb/utils.c                                 | 647 +++++++++++++++++++++++++++-
 gdb/utils.h                                 |   7 +-
 13 files changed, 1468 insertions(+), 125 deletions(-)