Move types that don't depend on template args our of spawn

This was reported by the LDC developers as being the source of an ICE
we are seeing on Windows.

source/geod24/LocalRest.d

@@ -103,6 +103,7 @@ module geod24.LocalRest;
 
 static import C = geod24.concurrency;
 import geod24.Serialization;
+import std.datetime.systime : Clock, SysTime;
 import std.format;
 import std.meta : AliasSeq;
 import std.traits : fullyQualifiedName, Parameters, ReturnType;
@@ -198,6 +199,58 @@ public class ClientException : Exception
     }
 }
 
+/// Simple exception unwind the stack when we need to terminate/restart,
+/// used by `spawn` but kept here as it doesn't depend on template parameters.
+private final class ExitException : Exception
+{
+    public bool restart;
+
+    this () @safe pure nothrow @nogc
+    {
+        super("You should never see this exception - please report a bug");
+    }
+}
+
+/// Wrapper for data inside of `spawn`, kept here as it doesn't
+/// depend on template parameters
+private struct Variant
+{
+    pure nothrow @nogc:
+
+    public this (Response res) @trusted
+    {
+        this.res = res;
+        this.tag = 0;
+    }
+    public this (Command cmd) @trusted
+    {
+        this.cmd = cmd;
+        this.tag = 1;
+    }
+
+    union
+    {
+        Response res;
+        Command cmd;
+    }
+
+    public ubyte tag;
+}
+
+/// Used by `spawn` for recording current filtering / sleeping setting
+private struct Control
+{
+    public FilterAPI filter;    // filter specific messages
+    public SysTime sleep_until; // sleep until this time
+    public bool drop;           // drop messages if sleeping
+
+    public bool isSleeping() const @safe /* nothrow: Not on Windows (currTime) */
+    {
+        return this.sleep_until != SysTime.init
+            && Clock.currTime < this.sleep_until;
+    }
+}
+
 /// Simple wrapper to deal with tuples
 /// Vibe.d might emit a pragma(msg) when T.length == 0
 private struct ArgWrapper (T...)
@@ -521,51 +574,9 @@ public final class RemoteAPI (API, alias S = VibeJSONSerializer!()) : API
         C.Tid self, string file, int line, CtorParams!Implementation cargs)
         nothrow
     {
-        import std.datetime.systime : Clock, SysTime;
         import std.algorithm : each;
         import std.range;
 
-        /// Simple exception unwind the stack when we need to terminate/restart
-        static final class ExitException : Exception
-        {
-            bool restart;
-
-            this () @safe pure nothrow @nogc
-            {
-                super("You should never see this exception - please report a bug");
-            }
-        }
-
-        // very simple & limited variant, to keep it performant.
-        // should be replaced by a real Variant later
-        static struct Variant
-        {
-            this (Response res) { this.res = res; this.tag = 0; }
-            this (Command cmd) { this.cmd = cmd; this.tag = 1; }
-
-            union
-            {
-                Response res;
-                Command cmd;
-            }
-
-            ubyte tag;
-        }
-
-        // used for controling filtering / sleep
-        static struct Control
-        {
-            FilterAPI filter;    // filter specific messages
-            SysTime sleep_until; // sleep until this time
-            bool drop;           // drop messages if sleeping
-
-            bool isSleeping() const
-            {
-                return this.sleep_until != SysTime.init
-                    && Clock.currTime < this.sleep_until;
-            }
-        }
-
         scope exc = new ExitException();
 
         void runNode ()