Increase coverage

CMakeLists: do not enforce strict prototypes on Windows.

On Windows, or at least when cross-built with Mingw-w64, build fails
because strict prototype fails on an included file (thus nothing we can
do about in json-c code):

> from /home/jehan/dev/src/json-c/json_util.c:44:
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:196:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
>   196 |   typedef INT_PTR (WINAPI *FARPROC) ();
>       |   ^~~~~~~
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:197:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
>   197 |   typedef INT_PTR (WINAPI *NEARPROC) ();
>       |   ^~~~~~~
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:198:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
>   198 |   typedef INT_PTR (WINAPI *PROC) ();
>       |   ^~~~~~~

Let's just disable the errors for Windows build.

Fix CMake tests for enforced strict prototypes.

Arraylist testcase

Enforce strict prototypes.

CMake: Install pkgconfig file in proper location by default

The default location for pkconfig files on most systems is:
  ${CMAKE_INSTALL_LIBDIR}/pkgconfig

Thus the file should get installed in there by default.

Be verbose on failing json_c_version test.

Test coverage for json_c_version.

Small cosmetics.

Small fixes to CMakeLists

Fix coveralls submission.

coveralls-cpp is dead and does not work anymore.
Fortunately there is coveralls-lcov available.

Linking with '-Bsymbolic-functions' is supported for ELF-binaries, only.

There was a typo in `CMAKE_SHARED_LINKER_FLAGS`.