TODO: remove deprecated form API items.

 1.9 Cache negative name resolves

 1.10 auto-detect proxy

 1.11 minimize dependencies with dynamically loaded modules

 1.12 have form functions use CURL handle argument

 1.14 Typesafe curl_easy_setopt()

 1.15 Monitor connections in the connection pool

 1.16 Try to URL encode given URL

 5.6 Refuse "downgrade" redirects

 5.7 Brotli compression

 5.8 QUIC

 5.9 Improve formpost API

 5.10 Leave secure cookies alone

 5.11 Chunked transfer multipart formpost

 6. TELNET

 6.1 ditch stdin

 18.2 glob posts

 18.3 prevent file overwriting

 18.4 simultaneous parallel transfers

 18.5 provide formpost headers

 18.6 warning when setting an option

 18.8 offer color-coded HTTP header output

 18.9 Choose the name of file in braces for complex URLs

 app/invoke/used protocols would be necessary to load.  See

 https://github.com/curl/curl/issues/349

1.12 have form functions use CURL handle argument

 curl_formadd() and curl_formget() both currently have no CURL handle

 argument, but both can use a callback that is set in the easy handle, and

 thus curl_formget() with callback cannot function without first having

 curl_easy_perform() (or similar) called - which is hard to grasp and a design

 mistake.

 The curl_formadd() design can probably also be reconsidered to make it easier

 to use and less error-prone. Probably easiest by splitting it into several

 function calls.

1.14 Typesafe curl_easy_setopt()

 One of the most common problems in libcurl using applications is the lack of

 implemented. This, to allow other projects to benefit from the work and to

 thus broaden the interest and chance of others to participate.

5.9 Improve formpost API

 Revamp the formpost API and making something that is easier to use and

 understand:

 https://github.com/curl/curl/wiki/formpost-API-redesigned

5.10 Leave secure cookies alone

 Non-secure origins (HTTP sites) should not be allowed to set or modify

 https://tools.ietf.org/html/draft-ietf-httpbis-cookie-alone-01

5.11 Chunked transfer multipart formpost

 For a case where the file is being made during the upload is progressing

 (like passed on stdin to the curl tool), we cannot know the size before-hand

 and we rather not read the entire thing into memory before it can start the

 upload.

 https://github.com/curl/curl/issues/1139

6. TELNET

 Using the multi interface would also allow properly using parallel transfers

 with HTTP/2 and supporting HTTP/2 server push from the command line.

18.5 provide formpost headers

 Extending the capabilities of the multipart formposting. How about leaving

 the ';type=foo' syntax as it is and adding an extra tag (headers) which

 works like this: curl -F "coolfiles=@fil1.txt;headers=@fil1.hdr" where

 fil1.hdr contains extra headers like

   Content-Type: text/plain; charset=KOI8-R"

   Content-Transfer-Encoding: base64

   X-User-Comment: Please don't use browser specific HTML code

 which should overwrite the program reasonable defaults (plain/text,

 8bit...)

18.6 warning when setting an option

 Display a warning when libcurl returns an error when setting an option.