[dmd-internals] More patches for severe bugs

[Don Clugston]

These two are wrong-code bugs which are a nightmare to debug since
they fail in subtle ways.

3560 foreach over nested function generates wrong code
3706 delegates of interfaces with multiple inheritance fail

There's actually not so many remaining severe wrong-code bugs -- most
of the worst ones were fixed in the past few releases.
There are a couple of others which I am still working on (I'm finding
them particularly difficult, which is why I've only got two in this
list).

I would also like to see this patch included in the next release,
since it abolishes a common bug from all D code.
4077 Bugs caused by bitwise operator precedence

There's at least a dozen other worthwhile patches in Bugzilla, but
none seem particularly urgent.