Rename interface agent, add shmem-dir option

The interface agent is renamed from interfaces.  Both agents now
accept the command-line option "--shmem-dir" to set the directory
where the Snabb shared memory segments reside.

subagent/Makefile.PL

@@ -10,7 +10,7 @@ WriteMakefile(
                            'NetSNMP::ASN' => '5.0.404',
                            'Net::SNMP' => '6.0.1',
                          },
-    EXE_FILES         => [ 'bin/interfaces', 'bin/pseudowire' ],
+    EXE_FILES         => [ 'bin/interface', 'bin/pseudowire' ],
     ABSTRACT          => 'AgentX-based SNMP sub-agent for Snabb applications',
     AUTHOR            => 'Alexander Gall <gall@switch.ch>',
     #LICENSE           => 'perl',

subagent/bin/interfaces → subagent/bin/interface

@@ -4,7 +4,7 @@ use warnings;
 use Getopt::Long;
 use Snabb::SNMP::Agent qw(%persistent_ifIndex %compound_scalar_handlers $sysUpTime);
 my %opt = ( 'check-interval' => 5,
-            'shmem-dir' => '/tmp/snabb-shmem', );
+            'shmem-dir' => '/var/lib/snabb/shmem', );
 
 sub usage() {
   print <<"EOF";
@@ -60,7 +60,7 @@ my %subtrees =
   );
 
 GetOptions(\%opt, "check-interval=i",
-           "ifindex=s") or usage();
+           "ifindex=s", "shmem-dir=s") or usage();
 defined $opt{ifindex} or usage();
 Snabb::SNMP::Agent::start({ name => "interfaces",
                             subtrees => \%subtrees,

subagent/bin/pseudowire

@@ -5,7 +5,7 @@ use Getopt::Long;
 use Snabb::SNMP::Agent qw(%persistent_ifIndex %compound_scalar_handlers);
 my %opt = ( 'check-interval' => 5,
             'mibs-dirs' => '',
-            'shmem-dir' => '/tmp/snabb-shmem');
+            'shmem-dir' => '/var/lib/snabb/shmem');
 
 sub usage() {
   print <<"EOF";
@@ -219,7 +219,7 @@ my %subtrees =
   );
 
 GetOptions(\%opt, "check-interval=i", "mibs-dirs=s",
-           "ifindex=s") or usage();
+           "ifindex=s", "shmem-dir=s") or usage();
 defined $opt{ifindex} or usage();
 Snabb::SNMP::Agent::start({ name => "pseudowire",
                             subtrees => \%subtrees,