DIGEST and HMAC were static variables. Those are initialized by
what ever concrete implementation gets executed first.

(Perform SCRAM-SHA1 first and those variables got initialized with
SHA1 variants)

For subsequent SHA256 executions those variables contained wrong
values.

after removing the ability to select and copy text the transformation methods
provided by CopyTextView are no longer necessary.

fixes #3940

maybe fixes #3924

note that the ROMs I tested this on don’t require scanning for it
to appear on MTP. However it certainly don’t hurt either.

- With large accounts (such as mine), Conversations starts hitting up against
  the default heap limit pretty quickly, at which point it grinds to a halt as
  GC pause times increase.
- Furthermore, it's impossible to complete a backup with such an account, since
  Conversations will just run out of memory before the backup can complete.
- Enabling the `android:largeHeap` flag asks the OS for a bit more memory, which
  hopefully alleviates the problem for larger accounts.

hopefully fixes #3890

An asterisk is a special FTS4 operator when appended to a word but has no
special meaning when prepended.

* various spelling fixes

- In some places, we weren't nulling out references to destroyed objects. This
  fixes that.
- (These were all discovered via LeakCanary instrumentation, and the fixes are
  hopefully rather straightforward-looking.)

- When the `viewHolder.messageBody` `TextView` created by a `MessageAdapter` is
  set to selectable, it leaks an `android.widget.Editor` (because that editor
  registers a view observer that never gets unregistered).
  - This memory leak is really quite problematic, as the message adapter is used
    a lot!
- Having the text be selectable is useless anyway, though; there isn't any way
  to select it (because long pressing just opens the context menu anyway).
  - It looks like the ListSelectionManager was meant to track selections across
    multiple messages. However, I'm not sure this feature ever gets used.
- Accordingly, this commit removes the entire feature, thus fixing the memory
  leak (since no `Editor` objects are ever created).
  - It should also reduce memory usage in general, since we aren't attaching an
    `Editor` to every single textview we create.
  - A `TextView` only allocates an `Editor` if you ask it to do certain things,
    like make the text selectable or register custom selection callbacks.