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

src/tool_ssls.c

@@ -85,7 +85,7 @@ CURLcode tool_ssls_load(struct OperationConfig *config,
 
     c = memchr(line, ':', strlen(line));
     if(!c) {
-      warnf("unrecognized line %d in ssl session file %s", i, filename);
+      warnf("unrecognized line %d in SSL session file %s", i, filename);
       continue;
     }
     *c = '\0';