Provide IRT process interface

src/untrusted/nacl/setpgid.c

Index: src/untrusted/nacl/setpgid.c
diff --git a/src/untrusted/nacl/chdir.c b/src/untrusted/nacl/setpgid.c
similarity index 63%
copy from src/untrusted/nacl/chdir.c
copy to src/untrusted/nacl/setpgid.c
index 2acc4c0aef86e239b0716259309e58622d9cde92..711356f5c9293e084e045c74b62fb67f32391be1 100644
--- a/src/untrusted/nacl/chdir.c
+++ b/src/untrusted/nacl/setpgid.c
@@ -10,13 +10,13 @@
 
 #include "native_client/src/untrusted/nacl/nacl_irt.h"
 
-int chdir(const char *path) {
-  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_filename.chdir,
-                             __libnacl_irt_dev_filename_init)) {
+int setpgid(pid_t pid, pid_t pgid) {
+  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_process.setpgid,
+                             __libnacl_irt_dev_process_init)) {
     return -1;
   }
 
-  int error = __libnacl_irt_dev_filename.chdir(path);
+  int error = __libnacl_irt_dev_process.setpgid(pid, pgid);
   if (error) {
     errno = error;
     return -1;