Consolidated the CMake project.

- Moved everything to one CMakeLists.txt
- Added support for the json_process test suites (instead of just the API
  tests).
- Changed to use the modified json_process version that does away with the
  environment variables (originally written by DanielT).
- Had to exclude "test_memory_funcs" on MSVC, since void pointer
  arithmetics are not allowed as it is done in secure_malloc and
  secure_free.
- Had to add a check for "ssize_t". This is not available on Windows and
  maybe on some other platforms (used in test_pack.c)
- Result from running ctest (The failure seems unrelated to CMake, it's
  just that the expected result is in a different order):
99% tests passed, 1 tests failed out of 121

Total Test time (real) =   1.31 sec

The following tests FAILED:
         24 - valid__complex-array (Failed)

test/suites/api/test_pack.c

@@ -6,6 +6,12 @@
  * it under the terms of the MIT license. See LICENSE for details.
  */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <jansson_config.h>
+
 #include <string.h>
 #include <jansson.h>
 #include <stdio.h>