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For completeness I've implemented escaping for characters outside the
basic multilingual plane, but it doesn't get used (as there's no
EscapeAsAsciiJson emitter option implemented).

Per https://cmake.org/cmake/help/latest/policy/CMP0091.html, we need to
enable policy CMP0091 if we want to make use of MSVC_RUNTIME_LIBRARY
and/or CMAKE_MSVC_RUNTIME_LIBRARY.  Fixes issue #912.

Fixes #740.

Inside of a sequence or map, `YAML::Newline` wouldn't reset the collection state, which would cause behavior like this:

```
nodeA:   
    k: [{i: 0},
 {i:1},
  ]NodeB:
    k: [{i: 0},
 {i:1},
  ]
```

* Support kinds of emitter format-setting for YAML::Null.

* update the code and test cases

* add the comment //fallthrough

* fix issue752: generate right long keys

* Improve the readability of test cases

* update to raw string literal

Found with modernize-use-auto
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with performance-unnecessary-value-param
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-container-size-empty
Signed-off-by: Rosen Penev <rosenp@gmail.com>

* partially fix clang compilation

Missing header and mistaken algorithm usage.

Also removed it name from range loops. It's not correct.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

* run through clang's -Wrange-loop-analysis

Some range loops should not use references as they need to copy.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

* manual range loop conversions
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-return-braced-init-list
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-inconsistent-declaration-parameter-name
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-bool-literals
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-raw-string-literal
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-emplace
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-using
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-override
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-equals-default
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-loop-convert
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-else-after-return
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Fix issue 844/848.

* spelling: differently

* spelling: irrelevant

* spelling: specified

Fixing issue 859.

Add test cases for the event handler for schema tags; does not include test cases for Node because specialized tag handling is not implemented yet.

The BadFile exception which is thrown when failing to open a file now
contains the filename.

Library debug postfix might not be suitable for cross platform project, and usually require extra work of link against prebuilt yaml-cpp.

Generally, Xcode project output library to these directories:
    Debug
    Release
    Debug-iphoneos
    Release-iphoneos
    Debug-iphonesimulator
    Release-iphonesimulator

Another Xcode project usually configured its build setting as follow, and expects library name to be same between Release and Debug
    LIBRARY_SEARCH_PATHS=$(CONFIGURATION)$(EFFECT_PLATFORM_NAME)
    OTHER_LDFLAGS= $(inherited) -lyaml-cpp

Fix invocation of clang-format in CMakeLists and apply clang-format.

Add Qt wrapper gist to README as a third party contribution 

This will allow hosting as Github Pages.