manifest: android-6.0.1_r81

This also reverts:

"Merge commit 'bbc9221' into master"
commit 243bbc686a8a20fbd70458da88ebb424a2f6ca40
(point external/sfntly back to aosp)

"Merge remote-tracking branch 'aosp/upstream-master' into master"
commit e78924fc97e4383be020fa7f51faa4f457fe2343
(point external/sfntly back to aosp)

"DO NOT MERGE - fix FTS3 column pointer handling"
commit b0216e4fbbb4690f534a9d3c0374aadd22940e47
(point external/sqlite back to aosp)

Further, point external/libavc back to aosp

Mentioned repos were updated in android-6.0.1_r81,
we don't have additions.

Change-Id: I9f525d824f9f5257d1b887f873a61912267657bf