Assert Type enum lower bound as well

Guard against min/max being macros in a cross-compiler way

Fix Windows doc build MSBuild error MSB6001

Sometimes, particularly when Microsoft's windows.h is included, min/max
are defined as macros, interfering with use of
std::numeric_limits::min() and the like.

To guard against this, the function name is wrapped in an extra set of
parenthesis, which inhibits function-style macro expansion.

When using a MSBuild-based CMake generator like 'Visual Studio 15 2017
Win64', the doc build was failing with the error 'MSB6001: Invalid
command line switch for "cmd.exe". Illegal characters in path.'

This was due to the dependency on Doxyfile*, which wasn't expanded by
CMake.

The fix is to expand this glob in CMake before specifying the custom
command's dependencies.

Partial fix for https://github.com/miloyip/rapidjson/issues/622

Specifies the endian of msvc ARM64 configuration.

Fix cross-compilation on certain toolchains

Allow Swap with ValueType

Update

Issue #1028: Visual Studio natvis file.

Fix #1017 allOf keyword fail with Writer handler

Gave up using static binding for null handler, because it cannot be
used with arbitrary handler type. Change `OutputHandler handler_` to
pointer type.

GenericStringRef: move assert out of expression

travis-doxygen.sh: upgrade to Doxygen 1.8.13

 * Upgrade to the latest Doxygen version 1.8.13
 * Drop unused variable DOXYGEN_BIN
 * Reenable --single-branch (travis-ci/travis-ci#5225 is closed)

Travis: Switch to Ubuntu 14.04 (Trusty)

Improve handling of NULL strings

ParseResult: improve bool conversion and add operator!=

Tutorial: fix typos in examples and broken links

 * Safely assert upon passing NULL string without length
   (requires usage of RAPIDJSON_ASSERT within an expression)
 * Allow using a NULL string together with an explicit length 0
   (GenericStringRef, GenericValue::SetString, ...), see #817
 * Add GenericValue::SetString(StringRefType, Allocator&) overload
 * Add tests for the various cases

 * Use safe-bool idiom for boolean conversion to avoid accidental
   misuse of ParseResult values (closes #989)
 * Add operator!= to support more comparison expressions
   (previously silently/erroneously used operator bool)

In the move example, the code uses `contacts` when the diagrams use
`contact` (no 's')

The code in the example:
```    Value contacts(kArrayType);
    // adding elements to contacts array.
    // ...
    o.AddMember("contacts", contacts, d.GetAllocator());  // deep clone contacts (may be with lots of allocations)
    // destruct contacts.
```