pgsql: Support building with Visual Studio 2015

Support building with Visual Studio 2015

Adjust the way we detect the locale. As a result the minumum Windows
version supported by VS2015 and later is Windows Vista. Add some tweaks
to remove new compiler warnings. Remove documentation references to the
now obsolete msysGit.

Michael Paquier, somewhat edited by me, reviewed by Christian Ullrich.

Backpatch to 9.5

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/0fb54de9aa4ffb792ea63af853146021ae501f12

Modified Files
--------------
doc/src/sgml/install-windows.sgml     | 29 +++++++++--------
src/backend/port/win32/crashdump.c    | 14 ++++++++
src/bin/pg_basebackup/pg_basebackup.c |  9 ++++--
src/include/port/win32.h              | 22 ++++++++++---
src/port/chklocale.c                  | 61 +++++++++++++++++++++++++++--------
src/port/win32env.c                   |  3 ++
src/tools/msvc/MSBuildProject.pm      | 23 +++++++++++++
src/tools/msvc/Solution.pm            | 26 +++++++++++++++
src/tools/msvc/VSObjectFactory.pm     | 12 +++++--
9 files changed, 165 insertions(+), 34 deletions(-)