Forks: Use a common fork list outside the EVMs

Many places outside the EVM use `Fork` and the fork list, and in general we
want progressively fewer dependencies on EVM internal types and files.

This may prove to be a temporary location, especially when we implement
issue #640.  But it's a fine temporary location if so.

Signed-off-by: Jamie Lokier <jamie@shareable.org>

nimbus/forks.nim

@@ -0,0 +1,19 @@
+# Nimbus - Enumerate Eth1 forks
+#
+# Copyright (c) 2018 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+# at your option. This file may not be copied, modified, or distributed except according to those terms.
+
+type
+  Fork* = enum
+    FkFrontier       = "frontier"
+    FkHomestead      = "homestead"
+    FkTangerine      = "tangerine whistle"
+    FkSpurious       = "spurious dragon"
+    FkByzantium      = "byzantium"
+    FkConstantinople = "constantinople"
+    FkPetersburg     = "petersburg"
+    FkIstanbul       = "istanbul"
+    FkBerlin         = "berlin"

nimbus/vm/interpreter/vm_forks.nim

@@ -1,20 +1,2 @@
-# Nimbus
-# Copyright (c) 2018 Status Research & Development GmbH
-# Licensed under either of
-#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
-#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
-# at your option. This file may not be copied, modified, or distributed except according to those terms.
-
-import stint, eth/common/eth_types
-
-type
-  Fork* = enum
-    FkFrontier = "frontier"
-    FkHomestead = "homestead"
-    FkTangerine = "tangerine whistle"
-    FkSpurious = "spurious dragon"
-    FkByzantium = "byzantium"
-    FkConstantinople = "constantinople"
-    FkPetersburg = "petersburg"
-    FkIstanbul = "istanbul"
-    FkBerlin = "berlin"
+import ../../forks
+export Fork

nimbus/vm2/interpreter/forks_list.nim

@@ -1,29 +1,2 @@
-# Nimbus
-# Copyright (c) 2018 Status Research & Development GmbH
-# Licensed under either of
-#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
-#    http://www.apache.org/licenses/LICENSE-2.0)
-#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
-#    http://opensource.org/licenses/MIT)
-# at your option. This file may not be copied, modified, or distributed except
-# according to those terms.
-
-## List of known Ethereum forks
-## ============================
-##
-## See `here <../../ex/vm/interpreter/forks_list.html>`_ for an
-## overview.
-
-type
-  Fork* = enum
-    FkFrontier = "frontier"
-    FkHomestead = "homestead"
-    FkTangerine = "tangerine whistle"
-    FkSpurious = "spurious dragon"
-    FkByzantium = "byzantium"
-    FkConstantinople = "constantinople"
-    FkPetersburg = "petersburg"
-    FkIstanbul = "istanbul"
-    FkBerlin = "berlin"
-
-# End
+import ../../forks
+export Fork