Don't re-export Func and Memory in extern.zig

src/extern.zig

@@ -1,11 +1,9 @@
 const Store = @import("./store.zig").Store;
+const Func = @import("./func.zig").Func;
 const FuncType = @import("./func.zig").FuncType;
+const Memory = @import("./memory.zig").Memory;
 const MemoryType = @import("./memory.zig").MemoryType;
 
-// Re-exported for convenience (for now).
-pub const Func = @import("./func.zig").Func;
-pub const Memory = @import("./memory.zig").Memory;
-
 /// Representation of a table in Wasmtime.
 pub const Table = extern struct {
     store_id: u64,

src/func.zig

@@ -3,14 +3,12 @@ const assert = std.debug.assert;
 const panic = std.debug.panic;
 
 const Store = @import("./store.zig").Store;
+const Extern = @import("./extern.zig").Extern;
+const Memory = @import("./memory.zig").Memory;
 const Diagnostics = @import("./diagnostics.zig").Diagnostics;
 const Error = @import("./error.zig").Error;
 const Trap = @import("./trap.zig").Trap;
 
-const _extern = @import("./extern.zig");
-const Extern = _extern.Extern;
-const Memory = _extern.Memory;
-
 const _val = @import("./val.zig");
 const Val = _val.Val;
 const ValType = _val.ValType;

src/instance.zig

@@ -1,6 +1,8 @@
 const Engine = @import("./engine.zig").Engine;
 const Module = @import("./module.zig").Module;
 const Store = @import("./store.zig").Store;
+const Func = @import("./func.zig").Func;
+const Memory = @import("./memory.zig").Memory;
 const Diagnostics = @import("./diagnostics.zig").Diagnostics;
 const Error = @import("./error.zig").Error;
 const Trap = @import("./trap.zig").Trap;
@@ -10,8 +12,6 @@ const Vec = @import("./vec.zig").Vec;
 const _extern = @import("./extern.zig");
 const Extern = _extern.Extern;
 const ExternType = _extern.ExternType;
-const Func = _extern.Func;
-const Memory = _extern.Memory;
 
 /// Representation of a instance in Wasmtime.
 ///