Upgrade dosbox solution and project to VS2019

Clean up project settings to prevent most MSVC linker warnings.
This commit also adds MSVC builds to CI.

src/platform/visualc/begin_code.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/begin_code.h>

src/platform/visualc/close_code.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/close_code.h>

src/platform/visualc/config.h

@@ -1,10 +1,10 @@
-#define VERSION "SVN"
+#define VERSION "staging"
 
 /* Define to 1 to enable internal debugger, requires libcurses */
 #define C_DEBUG 0
 
 /* Define to 1 to enable output=ddraw */
-#define C_DDRAW 1 
+#define C_DDRAW 1
 
 /* Define to 1 to enable screenshots, requires libpng */
 #define C_SSHOT 1

src/platform/visualc/sdl.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/SDL.h>

src/platform/visualc/sdl_endian.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/SDL_endian.h>

src/platform/visualc/sdl_opengl.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/SDL_opengl.h>

src/platform/visualc/sdl_thread.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/SDL_thread.h>

src/platform/visualc/sdl_version.h

@@ -0,0 +1,4 @@
+// This file exists only for MSVC builds.
+// It's needed because vcpkg does not set SDL subdirectory in includes list
+// for projects that do not use cmake.
+#include <SDL/SDL_version.h>