patch 8.2.0249: MS-Windows: various warnings

Problem:    MS-Windows: various warnings.
Solution:   Set the charset to utf-8. Add _WIN32_WINNT and _USING_V110_SDK71_.
            (Ken Takata, closes #5625)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index b95e936..da9a911 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -626,6 +626,12 @@
 NODEFAULTLIB = /nodefaultlib
 !endif
 
+# Specify source code charset to suppress warning C4819 on non-English
+# environment. Only available from MSVC 14.
+!if $(MSVC_MAJOR) >= 14
+CFLAGS = $(CFLAGS) /source-charset:utf-8
+!endif
+
 # Use multiprocess build on MSVC 10
 !if ("$(USE_MP)" == "yes") && ($(MSVC_MAJOR) >= 10)
 CFLAGS = $(CFLAGS) /MP
@@ -669,6 +675,9 @@
 
 CFLAGS = $(CFLAGS) $(OPTFLAG) -DNDEBUG $(CPUARG)
 RCFLAGS = $(rcflags) $(rcvars) -DNDEBUG
+! if "$(CL)" == "/D_USING_V110_SDK71_"
+RCFLAGS = $(RCFLAGS) /D_USING_V110_SDK71_
+! endif
 ! ifdef USE_MSVCRT
 CFLAGS = $(CFLAGS) /MD
 LIBC = msvcrt.lib