Problem:    Using old compiler on MS-Windows.
Solution:   Switch default build on MS-Windows to use MSVC 2015. (Ken Takata)

Problem:    win32.mak no longer included in Windows SDK.
Solution:   Do not include win32.mak. (Ken Takata)

Problem:    Cannot build with new MSVC version VS2017.
Solution:   Change the compiler arguments. (Leonardo Manera, closes #1731,
            closes #1747)

Problem:    Code for MS-Windows is complicated because of the exceptions for
            old systems.
Solution:   Drop support for MS-Windows older than Windows XP. (Ken Takata)

Problem:    Visual studio tools are noisy.
Solution:   Suppress startup info. (Mike Williams)

Problem:    Can't build GvimExt with SDK 7.1.
Solution:   Support using setenv.bat instead of vcvars32.bat. (Ken Takata)

Problem:    Building GvimExt with VS2015 may fail.
Solution:   Adjust the makefile. (Mike Williams)

Problem:    Cannot build GvimExt.
Solution:   Set APPVER to 5.0.  (KF Leong)

Problem:    Can't always find Win32.mak when building GvimExt.
Solution:   Use same mechanism as in Make_mvc.mak. (Cade Foster)