Closes https://github.com/curl/curl/pull/1153

... like 'user-agent = ""'

Adjusted test 71 to verify.

Since it now reads responses one byte a time, a loop could be removed
and it is no longer limited to get the whole response within 16K, it is
now instead only limited to 16K maximum header line lengths.

... as they broke with the cleaned up CONNECT handling

... so that it doesn't read data that is actually coming from the
remote. 2xx responses have no body from the proxy, that data is from the
peer.

Fixes #1132

A server MUST NOT send any Transfer-Encoding or Content-Length header
fields in a 2xx (Successful) response to CONNECT. (RFC 7231 section
4.3.6)

Also fixes the three test cases that did this.

Test 1281 added to verify

If a port number in a "connect-to" entry does not match, skip this
entry instead of connecting to port 0.

If a port number in a "connect-to" entry matches, use this entry
and look no further.

Reported-by: Jay Satiro
Assisted-by: Jay Satiro, Daniel Stenberg

Closes #1148

The function only exists since nghttp2 1.12.0.

Bug: https://github.com/curl/curl/commit/a4d8888#commitcomment-19985676
Reported-by: Michael Kaufmann

Closes #1125

Now all options are in the new system.

Moved over to the new format

There's mostly likely no need to allow setting SSLv2/3 version for HTTPS
proxy. Those protocols are insecure by design and deprecated.

Also define it in ILE/RPG binding.

Closes #1142

Add missing tests for CURLINFO_SCHEME, CURLINFO_PROTOCOL, %{scheme},
and %{http_version}

closes #1143

Follow-up to 4f8b1774

Sorted the lists too.

... and include the new ones in the PDF and HTML generation targets

Closes #1141

Prior to this change we depended on errno if strtol could not perform a
conversion. POSIX says EINVAL *may* be set. Some implementations like
Microsoft's will not set it if there's no conversion.

Ref: https://github.com/curl/curl/commit/ee4f7660#commitcomment-19658189

Ref: https://github.com/curl/curl/pull/1064#issuecomment-260052409

Follow-up to dbadaebf which changed the style.

- Restore the removed parts of the parameter check.

Follow-up to 945f60e8 which altered the parameter check.

Adds access to the effectively used protocol/scheme to both libcurl and
curl, both in string and numeric (CURLPROTO_*) form.

Note that the string form will be uppercase, as it is just the internal
string.

As these strings are declared internally as const, and all other strings
returned by curl_easy_getinfo() are de-facto const as well, string
handling in getinfo.c got const-ified.

Closes #1137