Add missing QLDocs

Author: owen-mc

go/ql/lib/semmle/go/Concepts.qll

@@ -539,6 +539,7 @@ module Cryptography {
 
   /** A data flow node that initializes a hash algorithm. */
   abstract class HashInit extends DataFlow::Node {
+    /** Gets the hash algorithm being initialized. */
     abstract HashingAlgorithm getAlgorithm();
   }
 
@@ -549,6 +550,7 @@ module Cryptography {
 
   /** A data flow node that initializes an encryption algorithm. */
   abstract class EncryptionInit extends DataFlow::Node {
+    /** Gets the encryption algorithm being initialized. */
     abstract EncryptionAlgorithm getAlgorithm();
   }
 
@@ -557,8 +559,10 @@ module Cryptography {
    * may also propagate taint for encryption algorithms.
    */
   abstract class BlockModeInit extends DataFlow::CallNode {
+    /** Gets the block cipher mode of operation being initialized. */
     abstract BlockMode getMode();
 
+    /** Gets a step propagating the encryption algorithm through this call. */
     abstract predicate step(DataFlow::Node node1, DataFlow::Node node2);
   }