Like frontend and backend options, encryption for memcached
connections is configured using tls keyword in
tls-session-cache-memcached and tls-ticket-key-memcached options.
tls-session-cache-memcached-tls and tls-ticket-key-memcached-tls
options are deprecated.

This change allows user to disable TLS per frontend address using
no-tls keyword in --frontend option.  We removed --frontend-no-tls in
favor of this new feature.

We added "tls" parameter to --backend option to enable TLS on that
backend connection.  --backend-tls options was deprecated, now is
noop.

This reverts commit 6680d8b7.

It was added because the default RelWithDebInfo type disabled
assertions, but now that -DNDEBUG is removed from its flags, it is not
necessary to change the build type anymore.

failmalloc and main tests succesfully pass the test now.

Fix Windows build by defining `ssize_t` when missing and adjusting the
install commands.

Add support for ENABLE_WERROR=1 while at it.

Tested with MSVC 2013 on Windows 7 x64.

Avoid adding a LIBXML2_LIBRARIES-NOTFOUND to the libraries list when it
is not found. Likewise for OpenSSL.

Matches autotools behavior. The m4_if logic was misread...

Do not add _U_ and NGHTTP2_NORETURN definitions to the command line,
instead add it to config.h. This matches what autotools does.

Users can disable this by setting -DCMAKE_C_FLAGS=-DNDEBUG or
-DCMAKE_CXX_FLAGS=-DNDEBUG to disable assertions as desired.

src/Makefile.am: fix missing allocator.h

Build type-specific flags are added before other flags, reflect this in
the output.