core, api: use "const char *" variables for result of string functions with const parameter

src/core/hook/hook-command.c

@@ -597,8 +597,8 @@ hook_command_exec (struct t_gui_buffer *buffer, int any_plugin,
     struct t_hook *hook_plugin, *hook_other_plugin, *hook_other_plugin2;
     struct t_hook *hook_incomplete_command;
     struct t_hook_exec_cb hook_exec_cb;
-    char **argv, **argv_eol, *command_name, *pos;
-    const char *ptr_string;
+    char **argv, **argv_eol, *command_name;
+    const char *ptr_string, *pos;
     int argc, rc, length_command_name, allow_incomplete_commands;
     int count_other_plugin, count_incomplete_commands, flags;
 

src/core/hook/hook-signal.c

@@ -132,7 +132,8 @@ void
 hook_signal_extract_flags (const char *signal, const char **ptr_signal,
                            int *stop_on_error, int *ignore_eat)
 {
-    char *pos, *str_flags, **flags;
+    const char *pos;
+    char *str_flags, **flags;
     int i, num_flags;
 
     if (!signal || !ptr_signal || !stop_on_error || !ignore_eat)