scripts: allow all perl scripts to be run directly

- Enable execute permission (chmod +x)

- Change interpreter to /usr/bin/env perl

Closes https://github.com/curl/curl/pull/2222

lib/checksrc.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 #***************************************************************************
 #                                  _   _ ____  _
 #  Project                     ___| | | |  _ \| |

lib/mk-ca-bundle.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 # ***************************************************************************
 # *                                  _   _ ____  _
 # *  Project                     ___| | | |  _ \| |
@@ -34,6 +34,7 @@ use Encode;
 use Getopt::Std;
 use MIME::Base64;
 use strict;
+use warnings;
 use vars qw($opt_b $opt_d $opt_f $opt_h $opt_i $opt_k $opt_l $opt_m $opt_n $opt_p $opt_q $opt_s $opt_t $opt_u $opt_v $opt_w);
 use List::Util;
 use Text::Wrap;