Missing SequencedExecutor.h

Summary:
When compiling using autoconf, automake, make and make install, SequencedExecutor.h is not installed automatically.
Closes https://github.com/facebook/folly/pull/799

Reviewed By: meyering

Differential Revision: D7241820

Pulled By: yfeldblum

fbshipit-source-id: 03c608c8ece2e7870a7bacce399ecc9455691948

folly/Makefile.am

@@ -101,6 +101,7 @@ nobase_follyinclude_HEADERS = \
 	executors/IOThreadPoolExecutor.h \
 	executors/NotificationQueueExecutor.h \
 	executors/ScheduledExecutor.h \
+	executors/SequencedExecutor.h \
 	executors/SerialExecutor.h \
 	executors/ThreadPoolExecutor.h \
 	executors/ThreadedExecutor.h \