Fix 2 small typos in comments

src/blockdata/block.rs

@@ -66,7 +66,7 @@ pub struct LoneBlockHeader {
     /// The actual block header
     pub header: BlockHeader,
     /// The number of transactions in the block. This will always be zero
-    /// when the LoneBlockHeader is returned as part ef a `headers` message.
+    /// when the LoneBlockHeader is returned as part of a `headers` message.
     pub tx_count: VarInt
 }
 

src/util/iter.rs

@@ -69,7 +69,7 @@ pub trait Pairable : Sized + Iterator {
 }
 
 impl<I: Iterator> Pairable for I {
-    /// Creates an iterator that yields pairs ef elements from the underlying
+    /// Creates an iterator that yields pairs of elements from the underlying
     /// iterator, yielding `None` when there are fewer than two elements to
     /// return.
     #[inline]