Few simple fixes that save RAM, as static strings are stored in RAM by default.

Marlin/Marlin.h

@@ -164,6 +164,7 @@ void Stop();
 bool IsStopped();
 
 void enquecommand(const char *cmd); //put an ascii command at the end of the current buffer.
+void enquecommand_P(const char *cmd); //put an ascii command at the end of the current buffer, read from flash
 void prepare_arc_move(char isclockwise);
 void clamp_to_software_endstops(float target[3]);