implement crypto.sha256 + some crypto cleanup

vlib/crypto/md5/md5.v

@@ -48,7 +48,7 @@ fn (d mut Digest) reset() {
 	d.len = u64(0)
 }
 
-// new returns a new hash.Hash computing the MD5 checksum.
+// new returns a new Digest (implementing hash.Hash) computing the MD5 checksum.
 pub fn new() *Digest {
 	mut d := &Digest{}
 	d.reset()

vlib/crypto/md5/md5block_generic.v

@@ -17,6 +17,7 @@ fn block_generic(dig &Digest, p []byte) {
 	mut b := dig.s[1]
 	mut c := dig.s[2]
 	mut d := dig.s[3]
+	
 	for i := 0; i <= p.len-BlockSize; i += BlockSize {
 		mut q := p.right(i)
 		q = q.left(BlockSize)