scripts: Switch to more portable Perl shebang

The default NetBSD package manager is pkgsrc and it installs Perl
along other third party programs under custom and configurable prefix.
The default prefix for binary prebuilt packages is /usr/pkg, and the
Perl executable lands in /usr/pkg/bin/perl.

This change switches "/usr/bin/perl" to "/usr/bin/env perl" as it's
the most portable solution that should work for almost everybody.
Perl's executable is detected automatically.

This change switches -w option passed to the executable with more
modern "use warnings;" approach. There is no functional change to the
default behavior.
Signed-off-by: NKamil Rytarowski <n54@gmx.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

scripts/checkpatch.pl

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 # (c) 2001, Dave Jones. (the file handling bit)
 # (c) 2005, Joel Schopp <jschopp@austin.ibm.com> (the ugly bit)
 # (c) 2007,2008, Andy Whitcroft <apw@uk.ibm.com> (new conditions, test suite)
@@ -6,6 +6,7 @@
 # Licensed under the terms of the GNU GPL License version 2
 
 use strict;
+use warnings;
 
 my $P = $0;
 $P =~ s@.*/@@g;

scripts/clean-header-guards.pl

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Clean up include guards in headers
 #
@@ -28,6 +28,7 @@
 #   "cc -E -DGUARD_H -c -P -", and fed the test program on stdin.
 
 use strict;
+use warnings;
 use Getopt::Std;
 
 # Stuff we don't want to clean because we import it into our tree:

scripts/cleanup-trace-events.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 # Copyright (C) 2013 Red Hat, Inc.
 #
 # Authors:

scripts/disas-objdump.pl

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
+
+use warnings;
 
 use File::Temp qw/ tempfile /;
 use Getopt::Long;

scripts/get_maintainer.pl

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 # (c) 2007, Joe Perches <joe@perches.com>
 #           created from checkpatch.pl
 #
@@ -11,6 +11,7 @@
 # Licensed under the terms of the GNU GPL License version 2
 
 use strict;
+use warnings;
 
 my $P = $0;
 my $V = '0.26';

scripts/shaderinclude.pl

-#!/usr/bin/perl
+#!/usr/bin/env perl
 use strict;
 use warnings;
 

scripts/switch-timer-api

-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use strict;
 use warnings;

scripts/texi2pod.pl

-#! /usr/bin/perl -w
+#! /usr/bin/env perl
 
 #   Copyright (C) 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
 
@@ -22,6 +22,8 @@
 # markup to Perl POD format.  It's intended to be used to extract
 # something suitable for a manpage from a Texinfo document.
 
+use warnings;
+
 $output = 0;
 $skipping = 0;
 %sects = ();