Improve the Windows installer readme text.

win_installer/readme.txt

@@ -1,14 +1,30 @@
-Simple Windows installer installing executable, license file and readme.txt to program
-files/cppcheck folder.
+Windows installer for the cppcheck
+----------------------------------
 
-Shortcuts are created to start cmd.exe in installation folder. So when 
-user selects start menu/desktop icon he gets command prompt in cppcheck 
-folder.
+Simple Windows installer installing executable, license file and readme.txt to
+program files/cppcheck folder.
 
-I'm just attaching the script file. Copy it to 'win_installer' -folder 
-in cppcheck folder. It expects to find ../Release/cppcheck.exe.
+Shortcuts are created to start cmd.exe in installation folder. So when the user
+selects start menu/desktop icon he gets command prompt in cppcheck folder.
 
 Get the InnoSetup from:
 http://www.innosetup.com/
 Be sure to download the 'QuickStart Pack' as it installs some nice tools
-like preprocessor support.
+like ISTool and preprocessor support.
+
+Files the installer needs:
+/Release/cppcheck.exe
+/COPYING
+/readme.txt
+
+Creating the installer executable:
+#1 Open the ISTool and load cppcheck.iss
+#2 Update the release version number:
+   - look for line "#define AppVersion"
+#3 Check all files are present:
+   - from menu: Project / Verify files...
+#4 Compile the installer
+   - from menu: Project / Compile Setup
+
+If compilation succeeds, the installer executable is created into folder
+/win_installer/output. The filename is cppcheck-[version]-setup.exe.