Fix parameter escape sequence parsing

We decoded "\\n" as "n" rather than "\n".
diff --git a/vncviewer/parameters.cxx b/vncviewer/parameters.cxx
index d24e5bc..448a243 100644
--- a/vncviewer/parameters.cxx
+++ b/vncviewer/parameters.cxx
@@ -253,7 +253,7 @@
         if (val[i+1] == replaceMap[j].second) {
           dest[pos] = replaceMap[j].first;
           escapedCharacter = true;
-          pos--;
+          i++;
           break;
         }
       }