Removing obsolete GDB 6.1.1 for FreeBSD 13

We currently have an obsolete version of GDB 6.1 installed as
/usr/libexec/gdb, kept only for use by crashinfo(8), which extracts
some basic information from a kernel core dump after a crash. If the
gdb port is installed crashinfo will use that in preference to
/usr/libexec/gdb. If neither exists it will not perform any analysis,
reporting "Unable to find a kernel debugger."

GDB 6.1.1 was released in June 2004 and is long obsolete. It does not
support all of the architectures that FreeBSD does, and imposes
limitations on the FreeBSD kernel build - the continued use of DWARF2.

I would like to remove GDB 6.1.1 before FreeBSD 13, and propose to
switch the GDB knob to default to NO in the near future. If the
crashinfo utility and related man pages do not already include
references to installing the gdb port/package I will add those before
making the change.

In the fullness of time we may use LLDB to extract the same
information, or provide other tooling to do so, but I do not want to
block GDB 6.1.1's removal on this.

Please let me know of any objections or comments.