Do not drop duplicated escape chars in case of non-macros

I don't see a reason why this should be done secretly. The responsible lines where introduces more than 8 years ago with d2f4d353 where the git history ends so I can't check the original intention.

On the other hand it causes troubled as I recently experienced with KAppTemplate. Where a string from a AndroidManifest.xml was rewritten and broke:

<meta-data android:name="android.app.use_local_qt_libs" android:value="-- %%USE_LOCAL_QT_LIBS%% --"/>

became

<meta-data android:name="android.app.use_local_qt_libs" android:value="-- %USE_LOCAL_QT_LIBS% --"/>