Pass non-trivial/large function args by reference

Fixes a bunch of `-Wclazy-function-args-by-ref` warnings. See
https://github.com/KDE/clazy/blob/master/docs/checks/README-function-args-by-ref.md
for details.

Most of these changes are automated, using the clazy fixit by setting
the `CLAZY_EXPORT_FIXES` before compilation and then running:

    $ mkdir /tmp/patch
    $ find ../src -iname "*.yaml" -exec mv {} /tmp/patch \;
    $ clang-apply-replacements /tmp/patch

1 files changed, 1 insertions, 1 deletions

diff --git a/src/engine/enginevumeter.h b/src/engine/enginevumeter.h
index a39da1bcc1..a1a94b75d1 100644
--- a/src/engine/enginevumeter.h
+++ b/src/engine/enginevumeter.h
@@ -8,7 +8,7 @@ class ControlProxy;
 class EngineVuMeter : public EngineObject {
     Q_OBJECT
   public:
-    EngineVuMeter(QString group);
+    EngineVuMeter(const QString& group);
     virtual ~EngineVuMeter();
 
     virtual void process(CSAMPLE* pInOut, const int iBufferSize);