badwords: rework exceptions, fix many of them

Also:
- support per-directory and per-upper-directory whitelist entries.
- convert badlist input grep tweak into the above format.
  (except for 'And' which had just a few hits.)
- fix many code exceptions, but do not enforce.
  (there also remain about 350 'will' uses in lib)
- fix badwords in example code, drop exceptions.
- badwords-all: convert to Perl.
  To make it usable from CMake.
- FAQ: reword to not use 'will'. Drop exception.

Closes #20886

lib/rtsp.c

@@ -433,7 +433,7 @@ static CURLcode rtsp_do(struct Curl_easy *data, bool *done)
     }
   }
 
-  /* The User-Agent string might have been allocated in url.c already, because
+  /* The User-Agent string might have been allocated already, because
      it might have been used in the proxy connect, but if we have got a header
      with the user-agent string specified, we erase the previously made string
      here. */
@@ -1011,7 +1011,7 @@ CURLcode Curl_rtsp_parseheader(struct Curl_easy *data, const char *header)
      *
      * Allow any non whitespace content, up to the field separator or end of
      * line. RFC 2326 is not 100% clear on the session ID and for example
-     * gstreamer does url-encoded session ID's not covered by the standard.
+     * gstreamer does URL-encoded session ID's not covered by the standard.
      */
     end = start;
     while((*end > ' ') && (*end != ';'))