Fix cmake not adding Werror on clang, and _lots_ of warnings (#4963)

* Fix cmake not adding Werror on clang, and _lots_ of warnings

* WIP: Build fixes

* Cannot make intermediate blockhandler instance

* Tiger's changes

* Fix BitIndex check

* Handle invalid NextState values in cMultiVersionProtocol

Co-authored-by: Tiger Wang <ziwei.tiger@outlook.com>

src/Protocol/ChunkDataSerializer.h

@@ -31,7 +31,7 @@ class cChunkDataSerializer
 		v401,
 		v477,
 
-		Count
+		Last = CacheVersion::v477
 	};
 
 	/** A single cache entry containing the raw data, compressed data, and a validity flag. */
@@ -79,7 +79,7 @@ protected:
 
 	/** A cache, mapping protocol version to a fully serialised chunk.
 	It is used during a single invocation of SendToClients with more than one client. */
-	std::array<ChunkDataCache, static_cast<size_t>(CacheVersion::Count)> m_Cache;
+	std::array<ChunkDataCache, static_cast<size_t>(CacheVersion::Last) + 1> m_Cache;
 } ;