reduced scope of some variables and avoided some copies

[firewave]

Another piece of preparation before applying misc-const-correctness fixes.

[firewave]

Hitting the known limitations of GCC 4.8 with initializer lists...

[firewave]

FYI I did some short profiling and I did not see any differences. So this is just about (c)leaner code.

[firewave]

I will also check if tickets need to be filed about the reduced variable scope.

The inconsistent copy vs. move in some of the calls in valueflow.cop will be cleaned up/clarified in another PR.

[firewave]

This is ready for merge now.