A common set of functions instead of many separate implementations for
creating buffers that can grow when appending data to them. Existing
functionality has been ported over.

In my early basic testing, the total number of allocations seem at
roughly the same amount as before, possibly a few less.

See docs/DYNBUF.md for a description of the API.

Closes #5300

This reduces the HTTP/2 window size to 32 MB since libcurl might have to
buffer up to this amount of data in memory and yet we don't want it set
lower to potentially impact tranfer performance on high speed networks.

Requires nghttp2 commit b3f85e2daa629
(https://github.com/nghttp2/nghttp2/pull/1444) to work properly, to end
up in the next release after 1.40.0.

Fixes #4939
Closes #4940

It could accidentally let the connection get used by more than one
thread, leading to double-free and more.

Reported-by: Christopher Reid
Fixes #4544
Closes #4557

There were a leftover few prototypes of Curl_ functions that we used to
export but no longer do, this removes those prototypes and cleans up any
comments still referring to them.

Curl_write32_le(), Curl_strcpy_url(), Curl_strlen_url(), Curl_up_free()
Curl_concat_url(), Curl_detach_connnection(), Curl_http_setup_conn()
were made static in 05b100aee247bb9bec8e9a1b0166496aa4248d1c.
Curl_http_perhapsrewind() made static in 574aecee208f79d391f10d57520b3.

For the remainder, I didn't trawl the Git logs hard enough to capture
their exact time of deletion, but they were all gone: Curl_splayprint(),
Curl_http2_send_request(), Curl_global_host_cache_dtor(),
Curl_scan_cache_used(), Curl_hostcache_destroy(), Curl_second_connect(),
Curl_http_auth_stage() and Curl_close_connections().

Closes #4096
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

urlapi: turn three local-only functions into statics

conncache: make conncache_find_first_connection static

multi: make detach_connnection static

connect: make getaddressinfo static

curl_ntlm_core: make hmac_md5 static

http2: make two functions static

http: make http_setup_conn static

connect: make tcpnodelay static

tests: make UNITTEST a thing to mark functions with, so they can be static for
normal builds and non-static for unit test builds

... and mark Curl_shuffle_addr accordingly.

url: make up_free static

setopt: make vsetopt static

curl_endian: make write32_le static

rtsp: make rtsp_connisdead static

warnless: remove unused functions

memdebug: remove one unused function, made another static

This is a companion patch to cbea2fd2c (NTLM: force the connection to
HTTP/1.1, 2018-12-06): with NTLM, we can switch to HTTP/1.1
preemptively. However, with other (Negotiate) authentication it is not
clear to this developer whether there is a way to make it work with
HTTP/2, so let's try HTTP/2 first and fall back in case we encounter the
error HTTP_1_1_REQUIRED.

Note: we will still keep the NTLM workaround, as it avoids an extra
round trip.

Daniel Stenberg helped a lot with this patch, in particular by
suggesting to introduce the Curl_h2_http_1_1_error() function.

Closes #3349

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

- replace tabs with spaces where possible
- remove line ending spaces
- remove double/triple newlines at EOF
- fix a non-UTF-8 character
- cleanup a few indentations/line continuations
  in manual examples

Closes https://github.com/curl/curl/pull/3037

- separate easy handle from connections better
- added asserts on a number of places
- added sanity check of pipelines for debug builds

Closes #2751

torture mode with test 1021 found it

Closes #1125