Added preliminary support for execve(). Updates to clone, fork, exit, task handling.

It turned out we used one version of kmalloc for malloc() and another for kfree()!
Now fixed.
Added parent-child relationship to tasks. Need to polish handling CLONE_PARENT and THREAD.

tasks/mm0/include/exec.h

@@ -0,0 +1,18 @@
+/*
+ * Definitions for executables
+ *
+ * Copyright (C) 2008 Bahadir Balban
+ */
+#ifndef __EXEC_H__
+#define __EXEC_H__
+
+/*
+ * This presents extra executable file information that is
+ * not present in the tcb, in a generic format.
+ */ 
+struct exec_file_desc {
+	unsigned long text_offset;	/* File offset of text section */
+	unsigned long data_offset;	/* File offset of data section */
+};
+
+#endif /* __EXEC_H__ */