Whole code base: various cleanups, removed SINGLE_SOURCE_COMPILE relicts

* cleaned up code and improved coding style
* removed old SINGLE_SOURCE_COMPILE macro relicts
* use QString::toUtf8() instead of QString::toAscii() wherever possible

(cherry picked from commit 0bb54199b0)

src/gui/widgets/text_float.cpp

@@ -1,5 +1,3 @@
-#ifndef SINGLE_SOURCE_COMPILE
-
 /*
  * text_float.cpp - class textFloat, a floating text-label
  *
@@ -198,4 +196,3 @@ void textFloat::updateSize( void )
 
 
 
-#endif