add d-exceptions compilation error regexp

[snosov1]

Hey!

This PR does 3 things:

• Adds a compilation error regexp that recognizes messages generated by the D runtime for unhandled exceptions (e.g. assert failures, like core.exception.AssertError@/tmp/app.d(10): unittest failure)
• Adds both ldc and the new d-exceptions rules to compilation-error-regexp-alist instead of suggesting to do so in the comment (does anyone read these comments?)
• Fixes the comments to be more positive (the stated uncertainties were verified)

[dmakarov]

I wrote these comments. I guess I didn't want to enforce on users the modifications to a customizable variable compilation-error-regexp-alist, but if someone wanted to use compilation mode with D, they could add the new symbol to the variable.

[snosov1]

I see your point. But in my opinion it should be the other way around. The vast majority of users will want it to be there by default and in rare cases this might not be desirable. So the users who don't want it should remove it.

[russel]

Can we come to a consensus on whether this should get committed to the mainline? We seems to have 1 for, 1 against, and 1 sitting on the fence (me :-).

[dmakarov]

Hi Russel,

In my opinion it's ok to commit.

[snosov1]

:+1: