++expecta/specta to arm64 branches

Conflicts:
	external/expecta
Remove test that boxes _Bool into NSValue
Removed traces of RACExtensions since they're part of the core framework now.
Merge pull request #978 from ReactiveCocoa/fix-bool-lifting

Fix _Bool lifting test
Merge pull request #982 from ReactiveCocoa/remove-traces-of-racextensions

Removed traces of RACExtensions since they're part of the core framework now.
Failing test case for #988, sometimes crashes with EXC_BAD_ACCESS
Code style & naming
Fixed -flatten: to not deallocate dequeueAndSubscribeIfAllowed while it's running.
Merge pull request #1 from ReactiveCocoa/flatten-last-sync-signal-bug

Fixed -flatten:.
Typo
Merge pull request #989 from corristo/flatten-last-sync-signal-bug

Fix and failing test case for #988
Failing testcase for #988
Another attempt to fix #988
Added Coursera class
Revert "Another attempt to fix #988"

This reverts commit 21a72a8b5fc09bdc2b5c8df5c6387c532dc52dc2.
Cherry-pick -flatten: from 3.0
Use `SEL` variable in RACSwizzleRespondsToSelector
Merge pull request #1006 from ReactiveCocoa/copy-3.0-flatten

Cherry-pick RAC 3.0's -flatten: into master
Add -[NSUserDefaults rac_channelTerminalForKey:]
RACSequence addition added to NSIndexSet