Check, after updating display, if viewport is really filled

Due to changed line heights, the rendered content might not reach to
the viewport bottom.

Issue #1147
Make line widget handles objects with methods. Handle widget height better

Closes #1147

Widget handles now have .clear() and .changed() methods. The second informs CodeMirror
that the widget changed, and causes it to recompute the line height for the widget's
line.

Fixes some sloppiness in the tracking of widget heights.
Don't set innerHTML in IE

It damages parent-child relationships in subnodes, which we might still
need later.
Make sure widgets are added to vertical scroll size

Closes #1148
Correct spelling from "givne" to "given".
Make temporary wheel measurement vars per-instance
Attach wheel measuring properties to display, not directly to CM instance

Issue #1151
widget.remove() should be widget.clear()
Add realtime.io to real-world uses
Remove improperly copy-pasted piece in mode/sieve/LICENSE
[test/mode_test.js] Remove some obsolete cruft
[tests] Overhaul mode testing framework

Tests are now specified in a less redundant format, and should be
easier to read and write.
Make the tester accurately report total test count

Even when a subset is selected.
Add MIHTool to real-world uses
Reinstate the fixedGutter option
Use document.documentMode when detecting IE versions

Closes #1149
Support Scala in GFM mode.
SearchCursor.matches() doesn't work properly if query is /.*/ issue #1155
Guard against search cursors with a query of ""

They'd exhibit the same infinite traversal behavior mentioned in
#1155
Improve Mode SQL

* mysql & mariadb:
** .21 syntax
** .table_name syntax
** added keywords
* MIMEs define their operatorChars
* MIMEs have a support prop
* use spaces as tab in index.html for consistency
* some return false -> null
* more comments