Add SPDX license identifiers to all Make/Kconfig files which:

 - Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

All files in lxdialog/ are licensed under GPL-2.0+, and the rest are
under GPL-2.0. I added GPL-2.0 tags to test scripts in tests/.

Documentation/process/license-rules.rst does not suggest anything
about the flex/bison files. Because flex does not accept the C++
comment style at the very top of a file, I used the C style for
zconf.l, and so for zconf.y for consistency.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

As in the unit test, the error message for the recursive inclusion
looks like this:

  Kconfig.inc1:4: recursive inclusion detected. Inclusion path:
    current file : 'Kconfig.inc1'
    included from: 'Kconfig.inc3:1'
    included from: 'Kconfig.inc2:3'
    included from: 'Kconfig.inc1:4'

The 'Kconfig.inc1:4' is duplicated in the first and last lines.
Also, the single quotes do not help readability.

Change the message like follows:

  Recursive inclusion detected.
  Inclusion path:
    current file : Kconfig.inc1
    included from: Kconfig.inc3:1
    included from: Kconfig.inc2:3
    included from: Kconfig.inc1:4

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

If recursive inclusion is detected, it should fail with error
messages.  Test this.

This also tests the line numbers in the error message, fixed by
commit 5ae6fcc4bb82 ("kconfig: fix line number in recursive inclusion
error message").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Ulf Magnusson <ulfalizer@gmail.com>