Introduce bundled directory

This is the first step of adding bundled Linux kernel UAPI headers for
compatibility purposes.  These headers are going to be copied verbatim
from the Linux kernel, they are provided by the Linux kernel under the
terms of the GNU General Public License version 2 only with an explicit
syscall exception.

According to analysis made by Kent Gibson at [1], we are allowed to
re-distribute unmodified Linux kernel UAPI headers under the same terms
as they are provided by the Linux kernel, and such re-distribution does
not affect the license of strace itself.

[1] https://lore.kernel.org/linux-gpio/20210128032641.GA11655@sol/

* bundled/Makefile.am: New file.
* configure.ac (AC_CONFIG_FILES): Add bundled/Makefile.
* Makefile.am (SUBDIRS): Add bundled.
* bundled/linux/GPL-2.0: New file, copied from Linux kernel
v5.10:LICENSES/preferred/GPL-2.0 file.
* bundled/linux/Linux-syscall-note: New file, copied from Linux kernel
v5.10:LICENSES/exceptions/Linux-syscall-note file.
* bundled/linux/COPYING: New file.
* COPYING: Mention it.

Thanks-to: Kent Gibson <warthog618@gmail.com>

COPYING

@@ -18,3 +18,9 @@ or FITNESS FOR A PARTICULAR PURPOSE.  See LGPL-2.1-or-later for more details.
 
 strace test suite is provided under the terms of the GNU General Public License
 version 2 or later, see tests/COPYING for more details.
+
+The `bundled/linux' directory contains some of Linux kernel UAPI header files
+copied verbatim from the Linux kernel for compatibility purposes.
+These header files are provided by the Linux kernel under the terms of the
+GNU General Public License version 2 only with an explicit syscall exception,
+see bundled/linux/COPYING for more details.

Makefile.am

@@ -15,7 +15,7 @@ endif
 if HAVE_MX32_RUNTIME
 TESTS_MX32 = tests-mx32
 endif
-SUBDIRS = src tests $(TESTS_M32) $(TESTS_MX32)
+SUBDIRS = bundled src tests $(TESTS_M32) $(TESTS_MX32)
 
 man_MANS = doc/strace.1 doc/strace-log-merge.1
 

bundled/Makefile.am

@@ -0,0 +1,12 @@
+# Automake input for bundled.
+#
+# Copyright (c) 2021 The strace developers.
+# All rights reserved.
+#
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+EXTRA_DIST = \
+	linux/COPYING \
+	linux/GPL-2.0 \
+	linux/Linux-syscall-note \
+	# end of EXTRA_DIST

bundled/linux/COPYING

@@ -0,0 +1,16 @@
+The `linux' directory contains some of Linux kernel UAPI header files
+copied verbatim from the Linux kernel for compatibility purposes.
+
+These header files are not a part of the strace project,
+they are provided by the Linux Kernel under:
+
+	SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
+
+Being under the terms of the GNU General Public License version 2 only,
+according with:
+
+	GPL-2.0
+
+With an explicit syscall exception, as stated at:
+
+	Linux-syscall-note

bundled/linux/Linux-syscall-note

@@ -0,0 +1,24 @@
+SPDX-Exception-Identifier: Linux-syscall-note
+SPDX-URL: https://spdx.org/licenses/Linux-syscall-note.html
+SPDX-Licenses: GPL-2.0, GPL-2.0+, GPL-1.0+, LGPL-2.0, LGPL-2.0+, LGPL-2.1, LGPL-2.1+, GPL-2.0-only, GPL-2.0-or-later
+Usage-Guide:
+  This exception is used together with one of the above SPDX-Licenses
+  to mark user space API (uapi) header files so they can be included
+  into non GPL compliant user space application code.
+  To use this exception add it with the keyword WITH to one of the
+  identifiers in the SPDX-Licenses tag:
+    SPDX-License-Identifier: <SPDX-License> WITH Linux-syscall-note
+License-Text:
+
+   NOTE! This copyright does *not* cover user programs that use kernel
+ services by normal system calls - this is merely considered normal use
+ of the kernel, and does *not* fall under the heading of "derived work".
+ Also note that the GPL below is copyrighted by the Free Software
+ Foundation, but the instance of code that it refers to (the Linux
+ kernel) is copyrighted by me and others who actually wrote it.
+
+ Also note that the only valid version of the GPL as far as the kernel
+ is concerned is _this_ particular version of the license (ie v2, not
+ v2.2 or v3.x or whatever), unless explicitly otherwise stated.
+
+			Linus Torvalds

configure.ac

@@ -814,6 +814,7 @@ AX_VALGRIND_DFLT([sgcheck], [off])
 AX_VALGRIND_CHECK
 
 AC_CONFIG_FILES([Makefile
+		 bundled/Makefile
 		 debian/changelog
 		 doc/strace.1
 		 doc/strace-log-merge.1