Fixed some problems:

files that use the em_code module must include the em_code.h file
improved checking of definitions after use
fixed problem with ranges in case statements

lang/m2/comp/error.c

@@ -20,6 +20,7 @@
 #include	<system.h>
 #include	<em_arith.h>
 #include	<em_label.h>
+#include	<em_code.h>
 
 #include	"strict3rd.h"
 #include	"input.h"