cosensus, core, eth, params, trie: fixes + clique history cap

consensus/clique/clique.go

consensus/clique/snapshot.go

consensus/ethash/sealer.go

core/blockchain.go

core/rawdb/database.go

core/rawdb/freezer.go

core/rawdb/freezer_table_test.go

eth/downloader/downloader.go

eth/downloader/downloader_test.go

eth/downloader/testchain_test.go

params/network_params.go

trie/sync_bloom.go