add support of --data-urlencode option

[rgilles]

--data-urlencode

(HTTP) This posts data, similar to the other --data options with the exception that this performs URL-encoding. (Added in 7.18.0)

To be CGI-compliant, the part should begin with a name followed by a separator and a content specification. The part can be passed to curl using one of the following syntaxes:

content

This will make curl URL-encode the content and pass that on. Just be careful so that the content doesn't contain any = or @ symbols, as that will then make the syntax match one of the other cases below!

=content

This will make curl URL-encode the content and pass that on. The preceding = symbol is not included in the data.

name=content

This will make curl URL-encode the content part and pass that on. Note that the name part is expected to be URL-encoded already.

@filename

This will make curl load data from the given file (including any newlines), URL-encode that data and pass it on in the POST.

name@filename

This will make curl load data from the given file (including any newlines), URL-encode that data and pass it on in the POST. >The name part gets an equal sign appended, resulting in name=urlencoded-file-content. Note that the name is expected to be URL-encoded already.