Protocol spec: use cmap package to attempt to improve search/copy-paste on some PDF readers.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -18,6 +18,8 @@
 }
 \fi
 
+% Load cmap before fontenc.
+\usepackage{cmap}
 \usepackage[utf8]{inputenc}
 \usepackage[T1]{fontenc}
 \usepackage{amsmath}
@@ -10868,6 +10870,13 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 \lsection{Change History}{changehistory}
 
 
+\historyentry{2020.1.16}{}
+\begin{itemize}
+    \item Attempt to improve search and cut-and-paste behaviour for ligatures in some
+          PDF readers.
+\end{itemize}
+
+
 \historyentry{2020.1.15}{2020-11-06}
 \begin{itemize}
     \item Add a missing consensus rule that has always been implemented in \zcashd: there