Revert "debugger: rename 'magic' prefix for custom dumper from qqDump to qdump__"

This reverts commit 136f3b8b.

tests/auto/debugger/tst_gdb.cpp

@@ -3616,7 +3616,6 @@ void breaker() {}
 
 int main(int argc, char *argv[])
 {
-    char *x = argv[0];
     #ifdef QT_GUI_LIB
     QApplication app(argc, argv);
     #else