pgsql: Add support for Visual Studio 2019 in build scripts

Add support for Visual Studio 2019 in build scripts

This adjusts the documentation and the scripts related to the versions
of Windows SDK supported.

Author: Haribabu Kommi
Reviewed-by: Andrew Dunstan, Juan José Santamaría Flecha, Michael
Paquier
Discussion: /messages/by-id/CAJrrPGcfqXhfPyMrny9apoDU7M1t59dzVAvoJ9AeAh5BJi+UzA@mail.gmail.com
Backpatch-through: 9.4

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/78aaffd285c4a66452004f8f2c4ff2771cee4cb4

Modified Files
--------------
doc/src/sgml/install-windows.sgml | 21 ++++++++-------
src/tools/msvc/MSBuildProject.pm | 25 ++++++++++++++++++
src/tools/msvc/README | 13 ++++-----
src/tools/msvc/Solution.pm | 28 ++++++++++++++++++++
src/tools/msvc/VSObjectFactory.pm | 55 +++++++++++++++++++++++++++++++--------
5 files changed, 115 insertions(+), 27 deletions(-)