fixed verify bug for VRAM and skip IO implementation

When verifying data in VRAM, the bank wrap check was executed
unconditionally, which caused verify errors if it reached address $c000.
New implementation: when loading large PRG files from 0801, it
skips now the IO area from $9f00 to $9fff, and loads the rest of
the program in banked RAM. Same implementation as already implemented
in C with LOAD_HYPERCALLS enabled, and with the "-prg" argument of the
emulator, see here:
commanderx16/x16-emulator#188

kernal/load.s

@@ -128,15 +128,24 @@ ld60	inc eal         ;increment store addr
 ;
 ;if necessary, wrap to next bank
 ;
-	lda eah
-	cmp #$c0        ;reached top of high ram?
-	bne ld64        ;no
 	lda verck       ;check mode
-	beq ld62        ;verify
 	bpl ld64        ;loading into vram
-ld62	lda #$a0        ;wrap to bottom of high ram
+	lda eah
+	cmp #$c0        ;reached top of high ram?
+	bne ld61        ;no
+	lda #$a0        ;wrap to bottom of high ram
 	sta eah
 	inc $9f61       ;move to next ram bank
+;
+;skip IO area
+;
+ld61	lda eah
+	cmp #$9f        ;reached top of low ram?
+	bne ld64        ;no
+	lda #$a0        ;skip to start of high ram
+	sta eah
+	lda #0
+	sta $9f61
 
 ld64	bit status      ;eoi?
 	bvc ld40        ;no...continue load