Currently, `-remove foo` would only remove an attribute `foo = ""`,
which doesn't work on an attribute like `src` that may have any
value. Extend `-remove` to handle both cases. `-remove foo=""` has
the old behavior, and `-remove foo` will remove the attribute with
whatever value it may have, which is still compatible with the old
behavior.
o Not all derived methods were marked 'override', but it is a great
feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
use the plain keyword going forward now that C++11 is established)
Claire Xenia Wolf
whitequark
Clifford Wolf
Henner Zeller