Here I attached a patch that supports building of PostgreSQL with VS 2019.
VS 2019 is going to release on Apr 2nd 2019, it will be good if version 12
supports compiling. The attached for is for review, it may needs some updates
once the final version is released.
Commit d9dd406fe281d22d5238d3c26a7182543c711e74 has reduced the
minimum visual studio support to 2013 to support C99 standards, because of this
reason, the current attached patch cannot be backpatched as it is.
I can provide a separate back branches patch later once this patch comes to a stage of commit. Currently all the supported branches are possible to compile with VS 2017.