#45 Prefer pass by reference instead of by value

[logzero]

Patch fixes pass by value cases spotted by cppcheck tool.

[logzero]

patch

[Klauss++]

You can't say

const std::string &blah = ""

That's troublesome, it has to either be explicitly cast to a string, or better yet, be a reference to a "std::string emptystring" somewhere

It's also not worth passing small objects by reference. Like in the collide hash table, T usually is a pointer.

I'm applying all except those.