++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
50 Shades of RACAction
Document private properties
Turn signal and generator constructors into categories
Generate the execution signal up front
Document all the RACtion that's happening
Use -and instead of a reduce block
Use a RACAction for UIRefreshControl