Allow 2-byte RELEXPR records to be used for branches of + or - 64KB.

Previously, the linker gave an error if the relative displacement was more than + or - 32 KB. But 2-byte RELEXPR records are typically used for the operand of the BRL instruction, and since its address calculation wraps around within the program bank, it can effectively address + or - 64KB (i.e. any location within the program bank). Similar reasoning applies to PER, the other instruction using long relative addressing.

This would give an error in code like the following:

bigbrl  start
        brl     later
        ds      33000  ; realistic examples would have actual code here
later   rtl
        end

(This currently also gives an assembler error due to similar logic in ORCA/M, but the output file can be linked anyway.)

This issue can affect very large functions compiled with ORCA/C or ORCA/Pascal, which may sometimes have branches that go more than 32 KB forward or back.

pass2.asm

@@ -1385,7 +1385,7 @@ lb2	lda	t1,X
 	blt	lb2
 	lda	t1-1,Y
 	bpl	lb6
-	bra	lb5
+	bra	lb4a
 lb3	lda	#$FF
 lb4	cmp	t1,X
 	bne	lb5
@@ -1394,6 +1394,9 @@ lb4	cmp	t1,X
 	blt	lb4
 	lda	t1-1,Y
 	bmi	lb6
+lb4a	lda	expLength	let BRL wrap around within program bank
+	cmp	#2
+	bge	lb6
 lb5	long	I,M
 	ph4	#0
 	ph2	#11