change the base64 before decoding. Updated to new base64
conventions.

Rev: src/nettle/testsuite/base64-test.c:1.4

and BASE64_DECODE_LENGTH. Updated test of base64_encode_raw (used
to be base64_encode).

Rev: src/nettle/testsuite/base64-test.c:1.3

in place.

Rev: src/nettle/testsuite/base64-test.c:1.2

Rev: src/nettle/testsuite/base64-test.c:1.1