initial support for Mega65 extra ROM

c64/basic/basic_execute_line.s

@@ -1,3 +1,5 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_BASIC_0)
+
 // Jump back into the BASIC execute line loop
 // after first checking that we have a colon
 // or $00 char
@@ -87,7 +89,7 @@ basic_execute_statement:
 
 	cmp #$7f
 	bcc not_a_token
-	// It's a token: So get the jump table entry for it, push it on the stack
+	// It is a token: So get the jump table entry for it, push it on the stack
 	// and then RTS to start it.
 	asl
 	tax
@@ -112,7 +114,7 @@ not_a_token:
 	cmp #$3a
 	beq basic_skip_char
 	
-	// If all else fails, it's a syntax error
+	// If all else fails, it is a syntax error
 	jmp do_SYNTAX_error
 
 basic_skip_char:
@@ -365,3 +367,6 @@ basic_command_jump_table:
 	.word cmd_unimplemented-1
 	.word cmd_unimplemented-1
 	.word cmd_unimplemented-1
+
+
+#endif // ROM layout