badwords: re-sync with curl-www, fix issues found

Also:
- replace `manpage` with `man page`, add to `badwords.txt`.
- badwords.pl: import `-w` feature from curl-www, syncing the two
  scripts fully.
- badwords.txt: import missing items from curl-www, syncing the two
  files fully.
- pyspelling.words: drop `cURL` allowed word.

Closes #19468

include/curl/easy.h

@@ -50,7 +50,7 @@ CURL_EXTERN void curl_easy_cleanup(CURL *curl);
  *
  * Request internal information from the curl session with this function.
  * The third argument MUST be pointing to the specific type of the used option
- * which is documented in each manpage of the option. The data pointed to
+ * which is documented in each man page of the option. The data pointed to
  * will be filled in accordingly and can be relied upon only if the function
  * returns CURLE_OK. This function is intended to get used *AFTER* a performed
  * transfer, all results from this function are undefined until the transfer

include/curl/multi.h

@@ -278,7 +278,7 @@ CURL_EXTERN const char *curl_multi_strerror(CURLMcode);
  * Desc:    An alternative version of curl_multi_perform() that allows the
  *          application to pass in one of the file descriptors that have been
  *          detected to have "action" on them and let libcurl perform.
- *          See manpage for details.
+ *          See man page for details.
  */
 #define CURL_POLL_NONE   0
 #define CURL_POLL_IN     1