mcexec: Add --stack-premap=<premap_size>[,<max>]

<premap_size> of stack is pre-mapped on creating a process.
And its max size of stack is set to <max>.
This replaces MCKERNEL_RLIMIT_STACK=<premap_size>,<max>.

executer/include/uprotocol.h

@@ -140,6 +140,7 @@ struct program_load_desc {
 	unsigned long mpol_flags;
 	unsigned long mpol_threshold;
 	unsigned long heap_extension;
+	long stack_premap;
 	int nr_processes;
 	char shell_path[SHELL_PATH_MAX_LEN];
 	__cpu_set_unit cpu_set[PLD_CPU_SET_SIZE];