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

tests/libtest/cli_hx_download.c

@@ -587,7 +587,7 @@ cleanup:
       }
       if(t->result)
         result = t->result;
-      else /* on success we expect ssl to have been checked */
+      else /* on success we expect SSL to have been checked */
         assert(t->checked_ssl);
     }
     curlx_free(transfer_d);

tests/libtest/first.h

@@ -103,7 +103,7 @@ void ws_close(CURL *curl);  /* just close the connection */
 #endif
 
 /*
- * TEST_ERR_* values must within the CURLcode range to not cause compiler
+ * TEST_ERR_* values must be within the CURLcode range to not cause compiler
  * errors.
  *
  * For portability reasons TEST_ERR_* values should be less than 127.

tests/libtest/lib3207.c

@@ -74,7 +74,7 @@ static unsigned int test_thread(void *ptr)
   int i;
 
   /* Loop the transfer and cleanup the handle properly every lap. This will
-     still reuse ssl session since the pool is in the shared object! */
+     still reuse SSL session since the pool is in the shared object! */
   for(i = 0; i < PER_THREAD_SIZE; i++) {
     CURL *curl = curl_easy_init();
     if(curl) {