tidy-up: miscellaneous

- fix typos and wording in documentation and comments.
- KNOWN_BUGS: merge duplicate H1 section.
- test_10_proxy: delete stray expressions.
- Perl: `while()` -> `while(1)`.
- Perl: fix indent, whitespace, drop redundant quotes and parentheses.
- fix casing: URL, SSL, Windows.
- badwords: readd `threadsafe`, add `well-known` (and fix it).
- replace `WinXP` -> `Windows XP` to match other uses.

Closes #21646

docs/libcurl/curl_easy_setopt.md

@@ -72,7 +72,7 @@ Passing in "creative octets" like newlines where they are not expected might
 trigger unexpected results.
 
 Before version 7.17.0, strings were not copied. Instead the user was forced
-keep them available until libcurl no longer needed them.
+to keep them available until libcurl no longer needed them.
 
 # OPTIONS
 

docs/libcurl/curl_multi_socket_action.md

@@ -92,7 +92,7 @@ to kickstart everything. To get one or more callbacks called.
 7. Wait for activity on any of libcurl's sockets, use the timeout value your
 callback has been told.
 
-8, When activity is detected, call curl_multi_socket_action() for the
+8. When activity is detected, call curl_multi_socket_action() for the
 socket(s) that got action. If no activity is detected and the timeout expires,
 call curl_multi_socket_action(3) with *CURL_SOCKET_TIMEOUT*.
 
@@ -103,7 +103,7 @@ call curl_multi_socket_action(3) with *CURL_SOCKET_TIMEOUT*.
 ~~~c
 int main(void)
 {
-  /* the event-library gets told when there activity on the socket 'fd',
+  /* the event-library gets told when there is activity on the socket 'fd',
      which we translate to a call to curl_multi_socket_action() */
   int running = 0;
   int fd = 3; /* the descriptor that had action */

docs/libcurl/opts/CURLOPT_SSL_CTX_DATA.md

@@ -30,7 +30,7 @@ CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void *pointer);
 
 # DESCRIPTION
 
-Data *pointer* to pass to the ssl context callback set by the option
+Data *pointer* to pass to the SSL context callback set by the option
 CURLOPT_SSL_CTX_FUNCTION(3), this is the pointer you get as third
 parameter.