Load external .so plugins

support for the Go 1.8 shared object feature of loading external
plugins.

this support relies on the developer defining a `Plugin` symbol in their
.so file that is a telegraf plugin interface.

So instead of the plugin developer "Adding" their own plugin to the
telegraf registry, telegraf loads the .so, looks up the Plugin symbol,
and then adds it if it finds it.

The name of the plugin is determined by telegraf, and is namespaced
based on the filename and path.

see #1717

CHANGELOG.md

@@ -56,7 +56,6 @@ be deprecated eventually.
 - [#2339](https://github.com/influxdata/telegraf/pull/2339): Increment gather_errors for all errors emitted by inputs.
 - [#2071](https://github.com/influxdata/telegraf/issues/2071): Use official docker SDK.
 - [#1678](https://github.com/influxdata/telegraf/pull/1678): Add AMQP consumer input plugin
-- [#2501](https://github.com/influxdata/telegraf/pull/2501): Support DEAD(X) state in system input plugin.
 
 ### Bugfixes
 

plugins/inputs/postgresql/README.md

@@ -30,21 +30,21 @@ _* value ignored and therefore not recorded._
 
 More information about the meaning of these metrics can be found in the [PostgreSQL Documentation](http://www.postgresql.org/docs/9.2/static/monitoring-stats.html#PG-STAT-DATABASE-VIEW)
 
-## Configuration
+## Configruation
 Specify address via a url matching:
 
   `postgres://[pqgotest[:password]]@localhost[/dbname]?sslmode=[disable|verify-ca|verify-full]`
 
 All connection parameters are optional. Without the dbname parameter, the driver will default to a database with the same name as the user. This dbname is just for instantiating a connection with the server and doesn't restrict the databases we are trying to grab metrics for.
-
+  
 A  list of databases to explicitly ignore.  If not specified, metrics for all databases are gathered.  Do NOT use with the 'databases' option.
 
   `ignored_databases = ["postgres", "template0", "template1"]`
-
+  
 A list of databases to pull metrics about. If not specified, metrics for all databases are gathered.  Do NOT use with the 'ignored_databases' option.
 
   `databases = ["app_production", "testing"]`
-
+  
 ### Configuration example
 ```
 [[inputs.postgresql]]

plugins/inputs/system/PROCESSES_README.md

@@ -23,7 +23,6 @@ it requires access to execute `ps`.
     - stopped
     - total
     - zombie
-    - dead
     - wait (freebsd only)
     - idle (bsd only)
     - paging (linux only)
@@ -40,7 +39,6 @@ Linux  FreeBSD  Darwin  meaning
   R       R       R     running
   S       S       S     sleeping
   Z       Z       Z     zombie
-  X      none    none   dead
   T       T       T     stopped
  none     I       I     idle (sleeping for longer than about 20 seconds)
   D      D,L      U     blocked (waiting in uninterruptible sleep, or locked)
@@ -56,5 +54,5 @@ None
 ```
 $ telegraf -config ~/ws/telegraf.conf -input-filter processes -test
 * Plugin: processes, Collection 1
-> processes blocked=8i,running=1i,sleeping=265i,stopped=0i,total=274i,zombie=0i,dead=0i,paging=0i,total_threads=687i 1457478636980905042
+> processes blocked=8i,running=1i,sleeping=265i,stopped=0i,total=274i,zombie=0i,paging=0i,total_threads=687i 1457478636980905042
 ```

plugins/inputs/system/processes.go

@@ -81,7 +81,6 @@ func getEmptyFields() map[string]interface{} {
 	case "openbsd":
 		fields["idle"] = int64(0)
 	case "linux":
-		fields["dead"] = int64(0)
 		fields["paging"] = int64(0)
 		fields["total_threads"] = int64(0)
 	}
@@ -108,8 +107,6 @@ func (p *Processes) gatherFromPS(fields map[string]interface{}) error {
 			fields["blocked"] = fields["blocked"].(int64) + int64(1)
 		case 'Z':
 			fields["zombies"] = fields["zombies"].(int64) + int64(1)
-		case 'X':
-			fields["dead"] = fields["dead"].(int64) + int64(1)
 		case 'T':
 			fields["stopped"] = fields["stopped"].(int64) + int64(1)
 		case 'R':
@@ -167,8 +164,6 @@ func (p *Processes) gatherFromProc(fields map[string]interface{}) error {
 			fields["blocked"] = fields["blocked"].(int64) + int64(1)
 		case 'Z':
 			fields["zombies"] = fields["zombies"].(int64) + int64(1)
-		case 'X':
-			fields["dead"] = fields["dead"].(int64) + int64(1)
 		case 'T', 't':
 			fields["stopped"] = fields["stopped"].(int64) + int64(1)
 		case 'W':