Add missing prototype for getpgid()

diff --git a/include/unistd.h b/include/unistd.h
index f1cde23..0b61d1a 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -17,6 +17,7 @@
 __extern pid_t fork(void);
 __extern pid_t vfork(void);
 __extern pid_t getpid(void);
+__extern pid_t getpgid(pid_t);
 __extern int setpgid(pid_t, pid_t);
 __extern pid_t getppid(void);
 __extern pid_t getpgrp(void);
diff --git a/klibc/include/unistd.h b/klibc/include/unistd.h
index f1cde23..0b61d1a 100644
--- a/klibc/include/unistd.h
+++ b/klibc/include/unistd.h
@@ -17,6 +17,7 @@
 __extern pid_t fork(void);
 __extern pid_t vfork(void);
 __extern pid_t getpid(void);
+__extern pid_t getpgid(pid_t);
 __extern int setpgid(pid_t, pid_t);
 __extern pid_t getppid(void);
 __extern pid_t getpgrp(void);