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.

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

NOTE: RelWithDebInfo *disables* assertions by default. To keep
assertions, use CMAKE_BUILD_TYPE=Debug or CMAKE_BUILD_TYPE=None.

Adds missing source files and configure.ac changes since
v1.7.0-93-g093eb51f.

Caught with cmake --warn-uninitialized.

libev 4.11 seems to build fine as demonstrated by Travis with autotools.

Add a "check" target that builds tests before running them.

Also fix useless MRUBY_LIBRARIES output and add the CMake build type
(e.g. Release, Debug, etc.)

libnghttp2.so was missing -fvisibility=hidden. libnghttp2_asio.so on the
other hand had hidden visibility which resulted in no exported symbols
and a broken asio client examples.

Just build a static nghttp2 library to solve this issue.

Warnings are useful, let's enable them by default.

Some detected libraries were not reported when a feature is disabled.
This change removes unnecessary second find_package calls and sets
HAVE_xxx immediately based on xxx_FOUND.

Auto-detect spdylay availability using CMake, making pkg-config
completely optional.

FindCython.cmake was taken from
https://github.com/thewtex/cython-cmake-example. The UseCython module
works, but since it is lacking an installation target setup.py will be
used instead.

mruby is always invoked now (mirrors the autotools behavior). It could
be optimized though to only trigger the mruby build when the static
library is missing.

Also fix typo in NGHTTP2_TESTS_DIR macro definition (detected when
invoking the Ninja generator).

Split the nghttp2 library into objects and a shared library from those
objects. This is needed because of symbol visibility. An advantage over
the autotools build is that there are no worries about static versus
static library builds.

Test:

    cmake $srcdir
    make nghttpx-unittest main failmalloc
    make test

Add auto-detection to the most important features (app, hpack, etc.).
Move options to a separate file for easier search.

Add cmake-based Libevent, jansson and CUnit search. Move pkg-config
handling for Libev and jemalloc to their cmake files.

Note: duplicates find_package before including CMakeOptions.txt and when
checking for features. Maybe that can be cleaned up later...

Remove build/host/target by a single target system name (CMake is
different for cross-compiling, you are suggested to set
CMAKE_TOOLCHAIN_FILE).

Fix various library variables, remove CFLAGS (INCLUDE_DIRS could be used
instead though, but I consider that minor information that could be
added later if wanted).

Fix various variable names (prefix, boost, etc.).

Might not be the best approach, maybe use thewtex/cython-cmake-example?