Merge Linux internal_clone() into internal_fork()

* defs.h (internal_clone): Remove.
* process.c (internal_clone): Merge into internal_fork().
(internal_fork) [!LINUX]: Remove dead code.
* syscall.c (internal_syscall): Replace internal_clone() with
internal_fork().
diff --git a/syscall.c b/syscall.c
index 3f551cd..16cbdcd 100644
--- a/syscall.c
+++ b/syscall.c
@@ -679,17 +679,15 @@
 #if defined(FREEBSD) || defined(LINUX) || defined(SUNOS4)
 	    || sys_vfork == func
 #endif
+#ifdef LINUX
+	    || sys_clone == func
+#endif
 #if UNIXWARE > 2
 	    || sys_rfork == func
 #endif
 	   )
 		return internal_fork(tcp);
 
-#if defined(LINUX) && (defined SYS_clone || defined SYS_clone2)
-	if (sys_clone == func)
-		return internal_clone(tcp);
-#endif
-
 	if (   sys_execve == func
 #if defined(SPARC) || defined(SPARC64) || defined(SUNOS4)
 	    || sys_execv == func