Catchain improvements (#698)

* Fix "sgn" in fift; fix marking infinite loops as noterurn in func

* TON-P1-1: Remove unused catchain queries

* TON-P1-15: Avoid synchronization with self

* TON-P1-3, TON-P1-17: Disallow more than one candidate per src per round (to prevent flood), add checks to process_broadcast

* TON-P1-10: Fix fast/slow attempts

* TON-P1-14: Add named constants

* TON-P1-18, TON-P1-19: Alloc temporary memory in the same way as persistent memory

* TON-P1-20: Add comment to choose_blocks_to_approve

* TON-P1-16: Avoid creating two catchain blocks on need_new_block

* TON-P1-8: Add some validation to validator-engine parameters

* TON-P1-6: Don't allow sending the same block many times

Many requests for the same block are not unusual (however, there's no need to answer them all)

* TON-P1-2: Enable prohibiting dependencies from blamed nodes (2.7.5 in CatChain doc), fix processing blame proofs

* Best practices

bp-6: Fix incorrect warning
bp-7: Remove unused code
bp-8: Bring back PerfWarningTimer logging (only when no callback)
bp-9: Remove unnecessary condition
bp-11: Remove commented-out code
bp-13: Divide code in validator-session-state
Adherence to Specification: Fix typo

doc/catchain.tex

@@ -243,7 +243,7 @@ Notice that an external punishment for creating catchain forks may be used in th
 Once a fork (created by~$i$) is detected (by another process~$j$), i.e.\ $j$ learns about two different messages $m_{i,s}$ and $m'_{i,s}$ created by $i$ and having same height $s$ (usually this happens while recursively downloading dependencies of some other messages), $j$ starts ignoring~$i$ and all of its subsequent messages. They are not accepted and not broadcast further. However, messages created by~$i$ prior to the fork detection may be still downloaded if they are referred to in messages (blocks) created by processes that did not see this fork before referring to such messages created by~$i$.
 
 \nxsubpoint\emb{Accepting messages from a ``bad'' process is bad}\label{sp:no.bad.accept}
-Furthermore, if process $i$ learns about a fork created by process $j$, then $i$ shows this to its neighbors by creating a new service broadcast message that contains the corresponding fork proof (cf.~\ptref{sp:fork.proofs}). Afterwards, this and all subsequent messages of $j$ cannot directly depend on any messages by the known ``bad'' producer $i$ (but they still can refer to messages from another party $k$ that directly or indirectly refer to messages of~$i$ if no fork by~$i$ was known to $k$ at the time when the referring message was created). If $j$ violates this restriction and creates messages with such invalid references, these messages will be discarded by all honest processes in the group.
+Furthermore, if process $i$ learns about a fork created by process $j$, then $i$ shows this to its neighbors by creating a new service broadcast message that contains the corresponding fork proof (cf.~\ptref{sp:fork.proofs}). Afterwards, this and all subsequent messages of $i$ cannot directly depend on any messages by the known ``bad'' producer $j$ (but they still can refer to messages from another party $k$ that directly or indirectly refer to messages of~$i$ if no fork by~$i$ was known to $k$ at the time when the referring message was created). If $i$ violates this restriction and creates messages with such invalid references, these messages will be discarded by all honest processes in the group.
 
 \nxsubpoint\emb{The set of ``bad'' group members is a part of the intrinsic state}\label{sp:bad.proc.set}
 Each process~$i$ keeps its own copy of the set of known ``bad'' processes in the group, i.e., those processes that have created at least one fork or have violated \ptref{sp:no.bad.accept}. This set is updated by adding~$j$ into it as soon as $i$ learns about a fork created by~$j$ (or about a violation of~\ptref{sp:no.bad.accept} by $j$); after that, a callback provided by the higher-level protocol is invoked. This set is used when a new broadcast message arrives: if the sender is bad, then the message is ignored and discarded.