a new java implementation of base64 for android-common

A new Base64 encoder/decoder class.  Some benchmarks comparing the
decoder it to those from android.os.Base64Utils (a decode-only native
implementation not accessible to apps) and
org.apache.commons.codec.binary.Base64, all with the JIT enabled:

  1k encoded data
  APACHE   avg:   811 us    min:   244 us    max: 13671 us
  COMMON   avg:   263 us    min:    30 us    max:  4730 us
  NATIVE   avg:   102 us    min:    61 us    max:  5493 us

  10k encoded data
  APACHE   avg:  3624 us    min:  2746 us    max: 23895 us
  COMMON   avg:   979 us    min:   518 us    max:  7751 us
  NATIVE   avg:   817 us    min:   762 us    max:  3143 us

  100k encoded data
  APACHE   avg: 33167 us    min: 31829 us    max: 140411 us
  COMMON   avg:  6047 us    min:  5493 us    max: 45227 us
  NATIVE   avg: 10109 us    min: 10009 us    max: 12451 us

Change-Id: Ic622e3a967a62d57d30bd25b80cbe4e0dd60e764
2 files changed