Fix unused variables

In almost all cases these can be removed. The only exception is in
ShaderViewer.cpp, where regIdx should have been used.

qrenderdoc/Code/CaptureContext.cpp

@@ -86,8 +86,6 @@ CaptureContext::CaptureContext(QString paramFilename, QString remoteHost, uint32
 
   if(!paramFilename.isEmpty())
   {
-    QFileInfo fi(paramFilename);
-
     m_MainWindow->LoadFromFilename(paramFilename, temp);
     if(temp)
       m_MainWindow->takeCaptureOwnership();