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

scripts/log2changes.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 # git log --pretty=fuller --no-color --date=short --decorate=full
 

scripts/updatemanpages.pl

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

scripts/zsh.pl

@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 # Generate ZSH completion