Propagate process labels to PD sessions

On Linux, we use the session label for naming the corresponding Linux
process. When looking up the processes via 'ps', the Genode process
hierarchy becomes immediately visible.

base/include/pd_session/connection.h

@@ -24,15 +24,11 @@ namespace Genode {
 		/**
 		 * Constructor
 		 *
-		 * \param args  additional session arguments
+		 * \param label  session label
 		 */
-		Pd_connection(const char *args = 0)
+		Pd_connection(const char *label = "")
 		:
-			Connection<Pd_session>(
-				session("ram_quota=4K%s%s",
-				        args ? ", " : "",
-				        args ? args : "")),
-
+			Connection<Pd_session>(session("ram_quota=4K, label=\"%s\"", label)),
 			Pd_session_client(cap())
 		{ }
 	};

base/src/base/process/process.cc

@@ -174,9 +174,10 @@ Process::Process(Dataspace_capability    elf_ds_cap,
                  Cpu_session_capability  cpu_session_cap,
                  Rm_session_capability   rm_session_cap,
                  Parent_capability       parent_cap,
-                 const char             *name,
+                 char const             *name,
                  char *const             argv[])
 :
+	_pd(name),
 	_cpu_session_client(cpu_session_cap),
 	_rm_session_client(rm_session_cap)
 {