fixed the famous 'SYS 64738', some documentation fixes

c64/kernal/interrupts/fce2.interop

@@ -0,0 +1,5 @@
+System reset routine has to be placed under it's original location due to 'SYS 64738' being extremaly popular to reset the C64,
+to the point it went into popular culture.
+
+https://twitter.com/hashtag/SYS64738?src=hash
+https://www.computerhope.com/jargon/s/sys64738.htm

c64/kernal/keyboard/scnkey_legacy.s

@@ -9,6 +9,11 @@
 //
 
 
+// NOTE: The code here is described as legacy, because the algorithm (although working very well)
+//       requires much more RAM than the original Kernal routine uses; without any form of extended
+//       RAM available to Open ROMs it will always be a serious compatibility risk.
+
+
 #if CONFIG_LEGACY_SCNKEY