Merge 2.10.x to master

Steps:

	% export MB=`git merge-base origin/2.10.x master`
	% git log --graph --oneline $MB...origin/2.10.x
	*   7d74884 Merge pull request #3181 from heathermiller/issue/6913
	|\
	| * 7063439 SI-6913 Fixing semantics of Future fallbackTo to be according to docs
	|/
	*   7c1d114 Merge pull request #3208 from dotta/si-7548-on-2.10
	|\
	| * 02308c9 SI-7458 Pres. compiler must not observe trees in silent mode
	| * 652b3b4 SI-7548 Test to demonstrate residual exploratory typing bug
	| * b7509c9 SI-7548 askTypeAt returns the same type whether the source was fully or targeted type-checked
	|/
	*   da73950 Merge pull request #3180 from xeno-by/topic/toolbox-rangepos
	|\
	| * 0c963c9 [nomaster] teaches toolbox about -Yrangepos
	* 5d9be8f Merge pull request #3196 from retronym/topic/3190-fixup

	% git merge -s ours da73950
	Merge made by the 'ours' strategy.

	% git log --grep SI-7458 --oneline

	% git merge 7c1d114
	CONFLICT (modify/delete): src/compiler/scala/tools/nsc/interactive/Global.scala deleted in HEAD and modified in 7c1d114. Version 7c1d114 of src/compiler/scala/tools/nsc/interactive/Global.scala left in tree.
	warning: inexact rename detection was skipped due to too many files.
	warning: you may want to set your merge.renamelimit variable to at least 1503 and retry the command.
	Automatic merge failed; fix conflicts and then commit the result.

	% git add .

	% git commit
	[merge-2.10.x-to-master 2c4ed0b] Merge commit '7c1d114' into merge-2.10.x-to-master

	% git merge 7d74884

	Auto-merging test/files/jvm/scala-concurrent-tck.scala
	CONFLICT (content): Merge conflict in test/files/jvm/scala-concurrent-tck.scala
	Auto-merging test/files/jvm/future-spec/PromiseTests.scala
	Auto-merging src/library/scala/concurrent/Future.scala
	warning: inexact rename detection was skipped due to too many files.
	warning: you may want to set your merge.renamelimit variable to at least 1503 and retry the command.
	Automatic merge failed; fix conflicts and then commit the result.

	% git commit