Drop compile-time deprecation warning

Fix POSITION_INDEPENDENT_CODE

The minimum version for the project is CMake 3.8.0, so there's
no point in keeping legacy code for pre-3.0 or pre-2.8 CMake.

Co-authored-by: Christopher Dunn <cdunn2001@gmail.com>

Fixes #1288

(creating merge-commit late, after accidental "rebase-and-merge")

 When the static libary is available use it as exported alias, otherwise use shared library. Cmake takes care about import library when Windows platform DLL is used

 - exported targets go to separate generated file and package config file generated from template to use automatic package resolving and resolution logic

 CMake  provides helpers to generate config file. Generated config file has usefull macro check_required_components() to set necessary variables like PackageName_FOUND if requirements has been satisfied. An absence of dedicated config file confuses user project as necessary variables are not set.

* slightly optimize Comments::set

Avoid allocation if the set is going to be rejected anyway.

Prototype suggestion from #1277 review thread

Use ArrayIndex instead of int.  Fixes #1266

* Fix Value::resize to fill all array elements

Fixes #1264

Disable also Visual Studio warning C4275 (std::exception used as base class in dll-interface class) when building as DLL and JSONCPP_DISABLE_DLL_INTERFACE_WARNING is defined.

Fixes #1249.

We should automate this, but for now we can at least update:

    make -f dev.makefile update-version
    make -f dev.makefile dox
    # Then, go to jsoncpp-doc repo, add, and push.

* https://github.com/open-source-parsers/jsoncpp-docs/issues/2

Also add two newlines

(rebased from `aaronfranke/formatting`)

resolves #1220
Co-authored-by: Aaron Franke <arnfranke@yahoo.com>

* Fix a precision bug of valueToString, prevent to give an error result on input of wanted precision 0 and a double value which end of zero before decimal point ,such as 1230.01,12300.1;
Add test cases for double valueToString with precision 0;

* Delete a test case with platform differences in the previous commit

* Fix clang-format.

* Fix clang-format!
Co-authored-by: lilei <dlilei@126.com>

* ENH: Prevent cmake in source builds

Building directly inside the root of the source tree
can cause problems where the build intermediate files
overwrite or conflict with the intended source code
files.

This modification identifies this problem and
issues failure messages and suggestions to over
come the problem with more robust build suggestion.
Co-authored-by: Jordan Bayles <jophba@chromium.org>

* Fix clang-tidy warnings
Signed-off-by: Marcel Opprecht <marcel.opprecht@scandit.com>

* Fixup/clang-format
Co-authored-by: Marcel Opprecht <marcel.opprecht@scandit.com>
Co-authored-by: Jordan Bayles <jophba@chromium.org>

Try meson/ninja from pypi

This lets us simplify linux a little.

However, we still want to test cmake, so there is only so much we
can simplify.

For OSX, we still need `clang-format` from homebrew.

* Add PYTHONUSERBASE/bin to PATH for linux