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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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/da52474f3d3cbdf38d8a6677a4ebedaf402ade3a

Modified Files
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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(-)