initial support for Mega65 extra ROM

c64/kernal/time/settim.s

@@ -1,9 +1,10 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
 
 //
 // Official Kernal routine, described in:
 //
-// - [RG64] C64 Programmer's Reference Guide   - page 299/300
-// - [CM64] Compute's Mapping the Commodore 64 - page 232
+// - [RG64] C64 Programmers Reference Guide   - page 299/300
+// - [CM64] Computes Mapping the Commodore 64 - page 232
 //
 // CPU registers that has to be preserved (see [RG64]): .A, .X, .Y
 //
@@ -11,7 +12,7 @@
 SETTIM:
 
 	// Disable interrupts for the duration of the routine, to prevent
-	// jiffy clock update while changing it's values
+	// jiffy clock update while changing its values
 	sei
 
 	// Store the jiffy clock state
@@ -25,3 +26,5 @@ SETTIM:
 	cli
 	rts
 
+
+#endif // ROM layout