Removing CSU patches

* Removed startup code patches in lib/csu regarding kernel to userland
   ABI.

 * Aligned stack layout on NetBSD stack layout.

 * Generate valid stack pointers instead of offsets by taking into account
   _minix_kerninfo->kinfo->user_sp.

 * Refactored stack generation, by moving part of execve in two
   functions {minix_stack_params(), minix_stack_fill()} and using them
   in execve(), rs and vm.

 * Changed load offset of rtld (ld.so) to:
      execi.args.stack_high - execi.args.stack_size - 0xa00000
   which is 10MB below the main executable stack.

Change-Id: I839daf3de43321cded44105634102d419cb36cec

kernel/system/do_exec.c

@@ -41,7 +41,8 @@ int do_exec(struct proc * caller, message * m_ptr)
   name[sizeof(name)-1] = '\0';
 
   /* Set process state. */
-  arch_proc_init(rp, (u32_t) m_ptr->PR_IP_PTR, (u32_t) m_ptr->PR_STACK_PTR, name);
+  arch_proc_init(rp, (u32_t) m_ptr->PR_IP_PTR, (u32_t) m_ptr->PR_STACK_PTR,
+	(u32_t) m_ptr->PR_PS_STR_PTR, name);
 
   /* No reply to EXEC call */
   RTS_UNSET(rp, RTS_RECEIVING);