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Coverity detected two "Memory - illegal accesses  (OVERRUN)" issues. Resizing the buffer should silence this warning.

closes #1824

Fix for #1647

Add restriction for tuple specialization of to_json

This commit fix the issue #1825
Signed-off-by: Camille Bégué <c.begue@samsung.com>

release: add singleinclude and meson.build to include.zip

appveyor.yml: Add MSVC 16 2019 support

Fix issue #1805

 * Add some restriction on pair partial specialization of to_json
Signed-off-by: Camille Bégué <camille.begue.pro@gmail.com>

Fix some spelling errors - mostly in comments & documentation.

I did not touch the Changelog file and any third party stuff.

additonal -> additional (1)
apppend -> append (2)
constuctor -> constructor (2)
contect -> context (2)
dobulequote -> doublequote (1)
elemnts -> elements (1)
exakt -> exact (2)
exluded -> exclude (1)
explicitely -> explicitly (2)
narcissic -> narcissistic (1)
ocurred -> occurred (1)
occuring -> occurring (2)
preceeds -> preceded (1)
ot -> to (2)
wehther -> whether (2)

Also call out to the guidelines for using pkg-config dependencies first,
and reference it for other build systems as well.

Although the possibility of installing with a pkg-config file is
somewhat hidden away in the meson docs, it's been deemed less invasive
due to not distracting away from cmake. So it will have to do.

This serves as a minimal release-only way to embed json into a project.
Add meson support to this directly, to make it usable standalone as a
meson subproject.

Implements #1672

iteration_proxy: Fix integer truncation from std::size_t to int

Update Hedley to v11.