Add gdb helpers script to help debugging

[cmcfarlen]

This script adds a data command to gdb so you can print out HttpSM data. This is a sort-of proof of concept for writing helper commands to help dig into ATS data structures. We can add more if we like this approach. I thought about using pretty-printers but those might be problematic so I went the custom command route so it doesn't otherwise interfere with debugging.

This requires at least gdb 10

[cmcfarlen]

(gdb) atspr sm this
smid = 229501
---- request ----
GET http://127.0.0.1/path/to/thing
Host: 127.0.0.1
Accept: text/plain, text/*, */*
Accept-Encoding: gzip
Connection: close
---- response ----
status: 403
Content-Type: text/plain
Cache-Control: no-cache
Content-Length: 0
Date: Mon, 12 Sep 2022 16:19:42 GMT
Age: 0
Connection: close
X-Cache: none
---- server_request  ----
GET :///path/to/thing
Host: 127.0.0.1
Accept: text/plain, text/*, */*
Accept-Encoding: gzip
Connection: close
X-Forwarded-For: 127.0.0.1
Connection: close
---- server_response  ----
status: 403
Content-Type: text/plain
Cache-Control: no-cache
Content-Length: 0
Date: Mon, 12 Sep 2022 16:19:42 GMT
---- transform_response  ----
invalid
---- cache_response  ----
invalid
---- client_info  ----
HTTP 1.1 (127.0.0.1 -> 127.0.0.1)
---- server_info  ----
HTTP 1.1 (127.0.0.1 -> 127.0.0.1)
---- parent_info  ----
HTTP 1.1 (127.0.0.1 -> 127.0.0.1)

[bneradt]

Looks helpful. Thanks for starting this.