std/*: add missing MIT license headers

lib/std/crypto/aegis.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("std");
 const mem = std.mem;
 const assert = std.debug.assert;

lib/std/crypto/aes_gcm.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("std");
 const assert = std.debug.assert;
 const builtin = std.builtin;

lib/std/crypto/bcrypt.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("std");
 const crypto = std.crypto;
 const fmt = std.fmt;

lib/std/crypto/hkdf.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("../std.zig");
 const assert = std.debug.assert;
 const hmac = std.crypto.auth.hmac;

lib/std/crypto/salsa20.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("std");
 const crypto = std.crypto;
 const debug = std.debug;

lib/std/io/auto_indenting_stream.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("../std.zig");
 const io = std.io;
 const mem = std.mem;

lib/std/io/change_detection_stream.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("../std.zig");
 const io = std.io;
 const mem = std.mem;

lib/std/io/find_byte_out_stream.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("../std.zig");
 const io = std.io;
 const assert = std.debug.assert;

lib/std/os/bits/linux/powerpc64.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 const std = @import("../../../std.zig");
 const linux = std.os.linux;
 const socklen_t = linux.socklen_t;

lib/std/os/linux/powerpc64.zig

@@ -1,3 +1,9 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
 usingnamespace @import("../bits.zig");
 
 pub fn syscall0(number: SYS) usize {