Adding info for generate.vbs settings to use SDL on VS project files

SDL_Win32.txt

@@ -7,12 +7,25 @@ However, it is possible using SDL libraries to improve the experience
  window size.
 
 
+Settings for Compiling
+----------------------
+You can edit generate.vbs script to preconfigure Visual Studio
+ project files (re)creation. Set at line 33:
+graph_config = "SDL"
+ or
+graph_config = "SDL2"
+Saving and launching vbscript you will obtain new VS project files
+ with correct included to solution files list.
+Then follow the steps below.
+
+
 Compiling SDL 1.2
 -----------------
 After setting up SDL 1.2 libraries, to successfully compile on MSVC,
  going to Project Properties (All Configurations):
 - on C/C++=>Preprocessor, set WITH_SDL into Preprocessor Definitions
-- on Linker=>System, set /SUBSYSTEM:WINDOWS or /SUBSYSTEM:CONSOLE
+- if you did not put "#undef main" directive on opendune.c source, go
+   on Linker=>System and set /SUBSYSTEM:WINDOWS or /SUBSYSTEM:CONSOLE
    (to define entry point on main for SDL)
 - on Linker=>Command Line, set /FORCE:MULTIPLE on Additional Options
    (to avoid 'multiple definitions' problems)
@@ -23,8 +36,9 @@ Compiling SDL 2.0
 After setting up SDL 2.0 libraries, to successfully compile on MSVC,
  going to Project Properties (All Configurations):
 - on C/C++=>Preprocessor, set WITH_SDL2 into Preprocessor Definitions
-- on Linker=>System, set /SUBSYSTEM:WINDOWS or /SUBSYSTEM:CONSOLE
-  (to define entry point on main for SDL)
+- if you did not put "#undef main" directive on opendune.c source, go
+   on Linker=>System and set /SUBSYSTEM:WINDOWS or /SUBSYSTEM:CONSOLE
+   (to define entry point on main for SDL)
 
 
 Additional Features