Correctly set default visibility on non-windows compilers

This fixes compilation of pugixml with -fvisibility=hidden. Without
this patch, one would get lots of unresolved symbols when consuming
pugixml as a shared library.

Enable usage of nullptr for MSVC 16 and newer (MSVS 2010)

... I forgot we still support platforms without C99, 23 years later.

sprintf now results in a deprecation warning in Xcode 14 beta.

Optimize compact mode

Fix memory leak during OOM in convert_buffer

This is the same fix as #497, but we're using auto_deleter instead
because if allocation function throws, we can't rely on an explicit call
to deallocate.

Comes along with two tests that validate the behavior.

Fix memory leak

tests: Fix MSVC 2022 build

Instead of trying to detect if we can safely use random shuffle simply reimplement it ourselves.
The quality of the RNG is not essential for these tests.

Also make sure the line shows up in grep when using the current version
number.

Fixes #478.

WinCE lacks most recent CRT additions to MSVC; we used to explicitly disable specific sections
of code, but it's more comprehensive to just specify that the CRT is from MSVC7 instead of MSVC8.

Fixes #401

Add support for Visual Studio 2022 with Platform Toolset v143.

Fixes #475

Set CMP0091 CMake policy

This allows the correct use of runtime library override.

Fixes #412

Add Cmake options for pugiconfig.hpp options

Fixes #387 
Closes #388 

Remove memory configuration options and rely on automatic detection of long long

The function returns true on success and false on failure.

Fix include in test_document.cpp when building against libc++. The _GLIBCXX_HAVE_UNISTD_H relies on pugixml and its tests being built against libstdc++, with LLVM's libc++ this won't be defined

Mark "project" check as information and disable "patch" check.

Store compile definitions in variable to avoid duplicated generator
expressions.

Moved needed defines to public section of target_compile_definitions.