RFC: String cleanup

[Daniel Marjamäki <daniel marjamaki comhem se>]

Hello friends!

I'm new to GTK, and would like to contribute. I have an idea for what I can do...

Changing from:
  [const] char *str
to:
  [const] char str[]
is often (but not always) a good idea because the latter is a more direct approach, saving both cpu and memory.

There are lots of places in GTK where I could make this change.

Any comments?

Best regards,
Daniel Marjamäki