Fix BigInteger.remainder check and BigInteger TODOsHEADlineage-18.1

Restore the BigInteger.remainder fallback test to check for small
results. Use RemainderKnuth if either the divisor or result is
short, as was done before. Checking for a short dividend doesn't
really make much sense, since that makes the result short as well.

Failed BN context allocations used to just pass null to the next
operation. Looking at the BN_mul implementation, it doesn't appear
that ends well. Explicitly check for that case.

Remove some potentially useful but unused methods from NativeBN.

Bug: 163898786
Test: Build and boot AOSP
Change-Id: I97a46199d8cf69acf29bcfc2f614c2205ff16262

0 files changed, 0 insertions, 0 deletions