.. also warn about letting the server pick the filename.

Reported-by: Bernard Spil

Current FAQ didn't make it clear where the main repo is.

Closes #612

The CURLOPT_SSH_PUBLIC_KEYFILE option has been documented to handle
empty strings specially since curl-7_25_0-31-g05a443a but the behavior
was unintentionally removed in curl-7_38_0-47-gfa7d04f.

This commit restores the original behavior and clarifies it in the
documentation that NULL and "" have both the same meaning when passed
to CURLOPT_SSH_PUBLIC_KEYFILE.

Bug: http://curl.haxx.se/mail/lib-2016-01/0072.html

Closes #514

- Add to both curl_global_init.3 and libcurl.3 the caveat for Windows
that initializing libcurl via a DLL's DllMain or static initializer
could cause a deadlock.

Bug: https://github.com/bagder/curl/issues/586


Reported-by:  <marc-groundctl@users.noreply.github.com>

This is the new command line option to set the value for the existing
libcurl option CURLOPT_EXPECT_100_TIMEOUT_MS

... and stick to 1.1 for HTTP. This is in line with what browsers do and
should have very little risk.

... and add a generic explanation for them instead. Each example file
should contain its own description these days.

Refer to _HEADERDATA not _WRITEDATA.

Reported-by: Michał Piechowski

pop3-multi.c:96:5: warning: implicit declaration of function 'memset'
imap-multi.c:96:5: warning: implicit declaration of function 'memset'
http2-download.c:226:5: warning: implicit declaration of function 'memset'
http2-upload.c:290:5: warning: implicit declaration of function 'memset'
http2-upload.c:290:5: warning: implicit declaration of function 'memset'

Moved some ideas from "next major" to just ordinary ideas since we can
always add new things while keeping the old without doing a "next
major".

Add error-checking to 'cd' in a few cases where omitting the checks
might result in an infinite loop.

Closes #535

Closes https://github.com/bagder/curl/pull/533

... if there are more than one using the same name