[trivial] Fix typos in comments

src/base58.h

@@ -147,7 +147,7 @@ public:
     K GetKey() {
         K ret;
         if (vchData.size() == Size) {
-            //if base58 encouded data not holds a ext key, return a !IsValid() key
+            // If base58 encoded data does not hold an ext key, return a !IsValid() key
             ret.Decode(&vchData[0]);
         }
         return ret;