improvements to HOST-RESOURCES-MIB::hrSWInstalled on debian systems

- add Install Date information instead of bogus 0-1-1
- include Arch in package names, like rpm output does
- use debian native separators `_` for package components, not rpm ones: `-`

to test:
snmpbulkwalk localhost HOST-RESOURCES-MIB::hrSWInstalled

Signed-Off-By: Elan Ruusamäe <glen@pld-linux.org>

--- net-snmp-5.7.3/agent/mibgroup/host/data_access/swinst_apt.c~	2016-04-23 17:40:44.000000000 +0300
+++ net-snmp-5.7.3/agent/mibgroup/host/data_access/swinst_apt.c	2016-04-23 17:40:49.740392789 +0300
@@ -22,6 +22,7 @@
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
 #endif
+#include <sys/stat.h>
 
 #include <net-snmp/net-snmp-includes.h>
 #include <net-snmp/agent/net-snmp-agent-includes.h>
@@ -29,8 +30,11 @@
 #include <net-snmp/library/snmp_debug.h>
 #include <net-snmp/data_access/swinst.h>
 
+netsnmp_feature_require(date_n_time)
+
 char pkg_directory[SNMP_MAXBUF];
 static char apt_fmt[SNMP_MAXBUF];
+static char file[SNMP_MAXBUF];
 
 /* ---------------------------------------------------------------------
  */
@@ -38,8 +42,8 @@
 netsnmp_swinst_arch_init(void)
 {
     strlcpy(pkg_directory, "/var/lib/dpkg/info", sizeof(pkg_directory));
-    snprintf(apt_fmt, SNMP_MAXBUF, "%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%ds",
-	SNMP_MAXBUF-1, SNMP_MAXBUF-1, SNMP_MAXBUF-1,
+    snprintf(apt_fmt, SNMP_MAXBUF, "%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%d[^#]#%%%ds",
+	SNMP_MAXBUF-1, SNMP_MAXBUF-1, SNMP_MAXBUF-1, SNMP_MAXBUF-1,
 	SNMP_MAXBUF-1, SNMP_MAXBUF-1, SNMP_MAXBUF-1);
 }
 
@@ -55,15 +59,19 @@
 int
 netsnmp_swinst_arch_load( netsnmp_container *container, u_int flags)
 {
-    FILE *p = popen("dpkg-query --show --showformat '${Package}#${Version}#${Section}#${Priority}#${Essential}#${Status}\n'", "r");
+    FILE *p = popen("dpkg-query --show --showformat '${Package}#${Version}#${Section}#${Priority}#${Essential}#${Architecture}#${Status}\n'", "r");
     char package[SNMP_MAXBUF];
     char version[SNMP_MAXBUF];
     char section[SNMP_MAXBUF];
     char priority[SNMP_MAXBUF];
     char essential[SNMP_MAXBUF];
+    char arch[SNMP_MAXBUF];
     char status[SNMP_MAXBUF];
     char buf[BUFSIZ];
+    struct stat stat_buf;
     netsnmp_swinst_entry *entry;
+    u_char *date_buf;
+    size_t date_len;
     int i = 0;
 
     if (p == NULL) {
@@ -78,20 +86,39 @@
             continue;   /* error already logged by function */
         CONTAINER_INSERT(container, entry);
 
-	sscanf(buf, apt_fmt, package, version, section, priority, essential, status);
+	sscanf(buf, apt_fmt, package, version, section, priority, essential, arch, status);
 	if (strstr(status, "not-installed"))
 	    continue;
 
         entry->swName_len = snprintf( entry->swName, sizeof(entry->swName),
-                                      "%s-%s", package, version);
+                                      "%s_%s_%s", package, version, arch);
 	if (entry->swName_len >= sizeof(entry->swName))
 	    entry->swName_len = sizeof(entry->swName)-1;
         entry->swType = (strcmp(essential, "yes") == 0)
                         ? 2      /* operatingSystem */
                         : 4;     /*  application    */
 
-        entry->swDate_len = 8;
-	memcpy(entry->swDate, "\0\0\1\1\0\0\0\0", 8);
+        /* get the last mod date */
+        snprintf(file, sizeof(file), "%s/%s.list", pkg_directory, package);
+        if(stat(file, &stat_buf) != -1) {
+            date_buf = date_n_time(&stat_buf.st_mtime, &date_len);
+            entry->swDate_len = date_len;
+            memcpy(entry->swDate, date_buf, entry->swDate_len);
+        } else {
+            /* somewhy some files include :arch in .list name */
+            snprintf(file, sizeof(file), "%s/%s:%s.list", pkg_directory, package, arch);
+            if(stat(file, &stat_buf) != -1) {
+                date_buf = date_n_time(&stat_buf.st_mtime, &date_len);
+                entry->swDate_len = date_len;
+                memcpy(entry->swDate, date_buf, entry->swDate_len);
+            }
+        }
+        /* FIXME, or fallback to whatever nonsesnse was here before, or leave it uninitialied?
+             else {
+            entry->swDate_len = 8;
+            memcpy(entry->swDate, "\0\0\1\1\0\0\0\0", 8);
+        }
+        */
     }
     pclose(p);
     DEBUGMSGTL(("swinst:load:arch"," loaded %d entries\n",