fix perl scripts to get perl bin from env

darshan-util/darshan-convert-logs.pl

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 
 #
 # Copyright (C) 2015 University of Chicago.
@@ -19,6 +19,8 @@
 #	jobid2	key1=val1	key2=val2
 #
 
+use warnings;
+
 my $darshan_convert = "./darshan-convert";
 my $jenkins_hash_gen = "./jenkins-hash-gen";
 

darshan-util/darshan-job-summary/bin/darshan-job-summary.pl.in

-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 #  (C) 2015 by Argonne National Laboratory.
 #      See COPYRIGHT in top-level directory.
@@ -7,6 +7,7 @@
 # Set via configure
 my $PREFIX="@prefix@";
 
+use warnings;
 use lib "@prefix@/lib";
 use TeX::Encode;
 use Encode;