already escaped backslash shouldn't escape the following quote in ConvertStringToArgs()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@54704 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/cmdline.cpp

@@ -1235,7 +1235,7 @@ wxArrayString wxCmdLineParser::ConvertStringToArgs(const wxChar *p)
                 break;
             }
 
-            lastBS = *p == _T('\\');
+            lastBS = !lastBS && *p == _T('\\');
 
             arg += *p;
         }