Specify the 100000-byte transaction size limit (pre-Overwinter).

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

protocol/protocol.tex

@@ -4285,6 +4285,8 @@ The encoding of $\joinSplitPubKey$ and the data to be signed are specified in
         on the Ed25519 curve, in the encoding specified by \cite{BDLSY2012}. Note that it is
         \emph{not} required that the encoding of the y-coordinate of the public key is
         less than $2^{255}-19$.
+  \prenuzeroitem{The encoded size of the \transaction{} \MUST be less than or equal to
+        $100000$ bytes.}
   \item \todo{Coinbase maturity rule.}
   \item \todo{Other rules inherited from \Bitcoin.}
 \end{consensusrules}
@@ -4337,6 +4339,8 @@ The changes relative to \Bitcoin version $1$ \transactions as described in \cite
         have been added.
   \item In \Zcash it is permitted for a \transaction to have no \transparent inputs provided
         that $\nJoinSplit > 0$.
+  \item A consensus rule limiting \transaction size has been added. In \Bitcoin there is
+        a corresponding standard rule but no consensus rule.
 \end{itemize}
 
 \sproutonly{
@@ -5498,6 +5502,8 @@ The errors in the proof of Ledger Indistinguishability mentioned in
 \subparagraph{2018.0-beta-7}
 
 \begin{itemize}
+    \item Specify the $100000$-byte limit on \transaction size.
+          (The implementation in \zcashd was as intended.)
     \item Rename $\mathsf{clamp}$ to $\mathsf{bound}$ and
           $\mathsf{ActualTimespanClamped}$ to $\ActualTimespanBounded$
           in the difficulty adjustment algorithm, to avoid a name