crypto.sha512, crypto.sha256 : Make public the `write()` and `sum()` methods (#13461)

vlib/crypto/sha256/sha256.v

@@ -90,7 +90,7 @@ pub fn new224() &Digest {
 }
 
 // write writes the contents of `p_` to the internal hash representation.
-fn (mut d Digest) write(p_ []byte) ?int {
+pub fn (mut d Digest) write(p_ []byte) ?int {
 	unsafe {
 		mut p := p_
 		nn := p.len

vlib/crypto/sha512/sha512.v

@@ -149,7 +149,7 @@ fn new384() &Digest {
 }
 
 // write writes the contents of `p_` to the internal hash representation.
-fn (mut d Digest) write(p_ []byte) ?int {
+pub fn (mut d Digest) write(p_ []byte) ?int {
 	unsafe {
 		mut p := p_
 		nn := p.len
@@ -183,7 +183,8 @@ fn (mut d Digest) write(p_ []byte) ?int {
 	}
 }
 
-fn (d &Digest) sum(b_in []byte) []byte {
+// sum returns the SHA512 or SHA384 checksum of digest with the data bytes in `b_in`
+pub fn (d &Digest) sum(b_in []byte) []byte {
 	// Make a copy of d so that caller can keep writing and summing.
 	mut d0 := *d
 	hash := d0.checksum()