Bug 971897: Use xpct{stubs,invoke}_x86_64 from linux/unix on OpenBSD/amd64 for consistency r=bsmedberg

This fixes the download panel issue, and brings us revs 727721e5d8ac,
844b142d8111 and 236989b3a807 as a bonus. Remove the unmaintained
OpenBSD/amd64 specific versions.
Merge m-c to m-i
Bug 1085321 - Remove gfxContext::Arc/NegativeArc. r=Bas
Bug 1088781 - Rename nsLayoutUtils::GetStringWidth to nsLayoutUtils::AppUnitWidthOfStringBidi. r=dholbert
Bug 1080688 - Calculate SVG rect bounds using a simple rect transform rather than using a Moz2D Path. r=longsonr
Bug 1076446 (attempt 2) - Make the DMD test work on Windows. r=glandium.
Bug 1014343 (attempt 2) - Add diff support to dmd.py. r=mccr8.
Bug 1085727 (part 1, attempt 2) - DMD: make some very short functions one-liners. r=mccr8.
Bug 1085727 (part 2, attempt 2) - Remove dmd.py's -b option and make its behaviour the default. r=mccr8.
Bug 1085727 (part 3, attempt 2) - Print dmd.py's invocation at the top of its output. r=mccr8.
Bug 1083071 - Avoid touching D3D11 at all, even to test if it works, if D3D11 layers are blacklisted. r=Bas, r=jmuizelaar
Backed out changeset 4d4abe4bee7f (bug 1083071) for bustage.
Bug 1083071 - Avoid touching D3D11 at all, even to test if it works, if D3D11 layers are blacklisted. r=Bas, r=jmuizelaar
Bug 1080302 (part 1) - Add support for --foo and /foo options where it's not already present. r=glandium.
Bug 1080302 (part 2) - Convert all mentions of -foo options to --foo options in comments, help messages and error messages. r=glandium.
Bug 1080302 (part 3) - Convert -foo options to --foo in |mach run|. r=glandium.
Bug 1087824 - Bump the limits some more. r=luke
No bug - Remove the executable bit from HTMLMediaElement.{h,cpp}.
Bug 1086510 - Remove set-only flags from HTMLContentSink; r=hsivonen
Bug 1089370 - Don't null-check a reference in nsContentUtils::CreateContextualFragment; r=jst
This triggers an undefined-bool-conversion warning in recent LLVM. The
dereference is safe because nsAutoTArray is infallible.