mincrypt: support SHA-256 hash algorithm

- adds a library to compute the SHA-256 hash

- updates the RSA verifier to take an argument specifying either SHA-1
  or SHA-256

- updates DumpPublicKey to with new "key" version numbers for
  specifying SHA-256

- adds new argument to adb auth code to maintain existing behavior

Change-Id: I5b1406cf57c2b8993f6032eda3e29139f7740839
Revert "mincrypt: support SHA-256 hash algorithm"

This reverts commit 6d34b5d4c0d378ff05d5f35617fec017d1a38666.