Closes #3548

Which was (possibly accidentally) dropped in the input style overhaul.

Closes #3555

Closes #3549

Issue #3548

Issue #3548

Issue #3525

Issue #3525

Issue #3536

I don't much care anymore, might move to semicolon-free style in future

So that the xu/msgenny modes can be dynamically loaded from meta.js

Issue #3523

Issue #3496

Issue #3542

In C++14, the single-quote character may be used arbitrarily
as a digit separator in numeric literals.

Closes #3538

Which wasn't taken into account in this input backend at all,
up to this point.

See http://discuss.codemirror.net/t/read-only-support-in-mobile-safari/470/1

Issue #3535

Issue #3518

Right now if you have a selection, and you enter a bracket/quote,
surrounds it with quotation marks, and selects the entire quote. This
change should change the behaviour to selecting the interior of the
quote instead.

The motivating example for me was autocomplete, where after
autocompleting a function the arguments are selected, so if you want
to insert a string literal right now you have to delete the selection
before you can enter the quotes. With the proposed fix, it'll be
rather more fluid.

Damaged in 1a56b954

For proper syntax highlighting

Closes #3512

Issue #3516

Since foo:bar was matching as a regex (as reported in #2521 but still
occurring for me), limit URI schemes to those in the CommonMark spec
for autolinks http://spec.commonmark.org/0.22/#autolinks

Closes #3513

Not 100% sure that this is the best way to deal with this - but if
you're in an expression, and encounter what you think is a type, it's
probably better to change your assumption and treat it as you would a
variable/constant (Because that's what it probably is) rather than to
forget everything.

I ran the test suite, and it didn't break anything, and the linter,
which was quiet.

Issue #3511