build: Removed old Visual Studio project files
build: Slight rename of new LIB_* makefile file variables

In order to try and be consistent between curl and libcurl renamed the
recently introduced LIB_* makefile file variables.
INSTALL: Updated for new Visual Studio project files
INSTALL: Updated MSVC 6 caveats

To use an up to date download link as well as remove duplicate
information.
Makefile.am: Fixed missing / in VC10+ project file generation
build-openssl.bat: Added default source directory when not specified

Added a default source directory so the user doesn't have to specify
one - the same as that, which the Visual Studio project files expect
the OpenSSL dependencies to be in.
build-openssl.bat: Added check for OpenSSL source directory
ALPN: fix typo in http/1.1 identifier

According to https://tools.ietf.org/html/draft-ietf-tls-applayerprotoneg-05
it is "http/1.1" and not "http/1.0".
http2: make connection re-use work

Http2 connections would wrongly get closed after each individual
request.

Co-authored-by: Tatsuhiro Tsujikawa
Bug: http://curl.haxx.se/bug/view.cgi?id=1374
README: Added some outstanding tasks to the TODO list

Added a couple of outstanding tasks to the TODO section that we didn't
get time to do before the release.
RELEASE-NOTES: synced with 85f4075bdbf3

Possibly the final update before release...
THANKS: 18 new contributors for 7.37.0
bump: Start working on the next release
build: Renamed CURLX_ONES file list definition to CURLX_CFILES

Renamed the CURLX_ONES file list definition in order to a) try and be
consistent with other file lists and b) to allow for the addition of
the curlx header files, which will assist with Visual Studio project
files generation rather than hard coding those files.
Makefile.inc: Added curlx headers to assist Visual Studio project generation
bits.close: introduce connection close tracking

Make all code use connclose() and connkeep() when changing the "close
state" for a connection. These two macros take a string argument with an
explanation, and debug builds of curl will include that in the debug
output. Helps tracking connection re-use/close issues.
bits.close: Fixed compilation warning

warning: implicit declaration of function 'connclose'
http.c: Fixed compilation warning

warning: suggest braces around empty body in an 'else' statement
Add support for --cacert in DarwinSSL.

Security Framework on OS X makes it possible to supply extra anchor (CA)
certificates via the Certificate, Key, and Trust Services API. This
commit makes the '--cacert' option work using this API.

More information:

https://developer.apple.com/library/mac/documentation/security/Reference/certifkeytrustservices/Reference/reference.html

The HTTPS tests now pass on OS X except 314, which requires the '--crl'
option to work.
darwinssl: fix lint & build warnings in the previous commit