Mentioned: https://curl.haxx.se/mail/lib-2020-01/0050.html

Closes #4814

- document the double-quote and backslash need be escaped if quoting.
- libcurl formdata escape double-quote in filename by backslash.
- curl formparse can parse filename both contains '"' and ',' or ';'.
- curl now can uploading file with ',' or ';' in filename.

Bug: http://curl.haxx.se/bug/view.cgi?id=1171

Consistently use CRLF instead. The mixed endings weren't
documented so I assume they were unintentional.

This change doesn't matter for curl itself but makes using
the tests with a proxy between curl and the test server
more convenient.

Tests that consistently use no carriage returns were
left unmodified as one can easily work around this.

It was introduced in commit eeb2cb05 along with the -F type=
change. Also fixed a typo in the name of the magic filename=
parameter. Tweaked tests 39 and 173 to better test this path.

are not, due mainly to the lack of support for XML character entities
(e.g. & => & ).  This will make it easier to validate test files using
tools like xmllint, as well as edit and view them using XML tools.

A) Normal non-proxy HTTP:

 - no more "Pragma: no-cache" (this only makes sense to proxies)

B) Non-CONNECT HTTP request over proxy:

 - "Pragma: no-cache" is used (like before)
 - "Proxy-Connection: Keep-alive" (for older style 1.0-proxies)

C) CONNECT HTTP request over proxy:

 - "Host: [name]:[port]"
 - "Proxy-Connection: Keep-alive"