to increase accuracy for quick transfers

Fixes #2200
Closes #2206

- Enable execute permission (chmod +x)

- Change interpreter to /usr/bin/env perl

Closes https://github.com/curl/curl/pull/2222

.. because limits.h presence isn't optional, it's required by C89.

Ref: http://port70.net/~nsz/c/c89/c89-draft.html#2.2.4.2

Closes https://github.com/curl/curl/pull/2215

- Free the copy of SSLKEYLOGFILE env returned by curl_getenv during ossl
  initialization.

Caught by ASAN.

This reverts commit c97648b5.

SIZEOF_LONG should not be checked in system.h since that macro is only
defined when building libcurl.

Ref: https://github.com/curl/curl/pull/2186#issuecomment-354767080
Ref: https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html

Reported-by: Pete Lomax
Bug: https://curl.haxx.se/mail/lib-2017-12/0074.html

Decoding loop implementation did not concern the case when all
received data is consumed by Brotli decoder and the size of decoded
data internally hold by Brotli decoder is greater than CURL_MAX_WRITE_SIZE.
For content with unencoded length greater than CURL_MAX_WRITE_SIZE this
can result in the loss of data at the end of content.

Closes #2194

- Ignore X509_R_CERT_ALREADY_IN_HASH_TABLE errors in the CTX callback
  since it's possible the cert may have already been loaded by libcurl.

- Remove the EXAMPLE code in the CURLOPT_SSL_CTX_FUNCTION.3 doc.
  Instead have it direct the reader to this cacertinmem.c example.

- Fix the CA certificate to use the right CA for example.com, Digicert.

Bug: https://curl.haxx.se/mail/lib-2017-12/0057.html
Reported-by: Thomas van Hesteren

Closes https://github.com/curl/curl/pull/2182

- Move the size modifier detection code from limit-rate to its own
  function so that it can also be used with max-filesize.

Size modifiers are the suffixes such as G (gigabyte), M (megabyte) etc.

For example --max-filesize 1G

Ref: https://curl.haxx.se/mail/archive-2017-12/0000.html

Closes https://github.com/curl/curl/pull/2179

Closes https://github.com/curl/curl/pull/2186

Closes https://github.com/curl/curl/pull/2185

Move curl_mime_initpart() and curl_mime_cleanpart() calls to lower-level
functions dealing with UserDefined structure contents.
This avoids memory leakages on curl-generated part mime headers.
New test 2073 checks this using the cli tool --next option: it
triggers a valgrind error if bug is present.

Bug: https://curl.haxx.se/mail/lib-2017-12/0060.html
Reported-by: Martin Galvan

- When zlib version is < 1.2.0.4, process gzip trailer before considering
extra data as an error.
- Inflate with Z_BLOCK instead of Z_SYNC_FLUSH to maximize correct data
and minimize corrupt data output.
- Do not try to restart deflate decompression in raw mode if output has
started or if the leading data is not available anymore.
- New test 232 checks inflating raw-deflated content.

Closes #2068

Some error codes were not yet defined in brotli 0.6.0: do not issue code
for them in this case.

Bug: #2175

[ci skip]

scan-build would warn on a potential access of an uninitialized
buffer. I deem it a false positive and had to add this somewhat ugly
work-around to silence it.

A scan-build warning.

This broke in 07cb27c9. Make sure to return 'result' properly. Pointed
out by scan-build!

Bug: #2174

Follow-up to c92d2e14

Closes #2172

... to make it clearer that the options want address-only, while the
headers in an email can also have the real name.

Assisted-by: Sean MacLennan

... as I reran the contrithanks script after the mailmap name fixups.

... for the CURLOPT_TIMEOUT, CURLOPT_CONNECTTIMEOUT and
CURLOPT_SERVER_RESPONSE_TIMEOUT range checks.

Reported-by: Dominik Hölzl
Bug: https://curl.haxx.se/mail/lib-2017-12/0037.html

Closes #2173

Fixed undefined symbol of getenv() which does not exist when compiling
for Windows 10 App (CURL_WINDOWS_APP). Replaced getenv() with
curl_getenv() which is aware of getenv() absence when CURL_WINDOWS_APP
is defined.

Closes #2171

Suggested-by: Rainer Canavan

Closes #2126