Specify the maximum block size. fixes #91

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

protocol/protocol.tex

@@ -3123,6 +3123,7 @@ be the constant defined in \crossref{constants}.
   \item \solution{} \MUST represent a valid Equihash solution as defined in \crossref{equihash}.
   \item \nTimeField{} \MUST be strictly greater than the median time of the previous
         $\PoWMedianBlockSpan$ \blocks.
+  \item The size of a \block{} \MUST be less than or equal to 2000000 bytes.
   \item \todo{Other rules inherited from \Bitcoin.}
 \end{consensusrules}
 
@@ -3141,6 +3142,7 @@ The changes relative to \Bitcoin version 4 blocks as described in \cite{Bitcoin-
         by hard forks), that it will be parseable according to this format.
   \item The $\hashReserved$, $\solutionSize$, and $\solution$ fields have been added.
   \item The type of the $\nNonce$ field has changed from \type{uint32\_t} to \type{char[32]}.
+  \item The maximum \block size has been doubled to 2000000 bytes.
 \end{itemize}
 
 \begin{pnotes}
@@ -4037,6 +4039,7 @@ The errors in the proof of Ledger Indistinguishability mentioned in
 
 \begin{itemize}
     \item $\MerkleHashLength$ is a bit length, not a byte length.
+    \item Specify the maximum \block size.
 \end{itemize}
 
 \introlist