fix irq related crash by no longer zeroing out stored vector

compiler/res/prog8lib/conv.p8

@@ -6,7 +6,7 @@ conv {
 
 ; ----- number conversions to decimal strings ----
 
-    ubyte[16]  @shared string_out       ; result buffer for the string conversion routines
+    ubyte[16]  @shared string_out       ; result buffer for the string conversion routines (note: uses uninitialized ARRAY instead of STR, to force it to be allocated in BSS area so it's ROM-compatible)
 
     asmsub str_ub0(ubyte value @A) clobbers(X) -> str @AY {
         ; ---- convert the ubyte in A in decimal string form, with left padding 0s (3 positions total)

compiler/res/prog8lib/cx16/syslib.p8

@@ -1474,9 +1474,9 @@ asmsub  restore_irq() clobbers(A) {
 	    sta  cx16.VERA_IEN
 	    cli
 	    rts
-        .section BSS
+        .section BSS_NOCLEAR
 _orig_irqvec    .word  ?
-        .send BSS
+        .send BSS_NOCLEAR
         ; !notreached!
     }}
 }

compiler/res/prog8lib/prog8_lib.asm

@@ -1,9 +1,9 @@
 ; Internal library routines - always included by the compiler
 ; Generic machine independent 6502 code.
 
-		.section BSS
+		.section BSS_NOCLEAR
 orig_stackpointer	.byte  ?	; stores the Stack pointer register at program start
-		.send BSS
+		.send BSS_NOCLEAR
 
 program_startup_clear_bss    .proc
 	; this is always ran first thing from the start routine to clear out the BSS area