Fix codegen error for some indirect accesses to 64-bit values.

The code was not properly adding in the offset of the 64-bit value from the pointed-to location, so the wrong memory location would be accessed. This affected indirect accesses to non-initial structure members, when used as operands to certain operations.

Here is an example showing the problem:

#include <stdio.h>

long long x = 123456;

struct S {
        long long a;
        long long b;
} s = {0, 123456};

int main(void) {
        struct S *sp = &s;

        if (sp->b != x) {
                puts("error");
        }
}

Gen.pas

@@ -321,6 +321,7 @@ case op^.opcode of
          loc := LabelToDisp(op^.left^.r) + op^.left^.q;
       if (op^.left^.opcode <> pc_lod) or (loc > 255) then
          Error(cge1);
+      offset := offset + op^.q;
       if offset = 0 then
          GenNative(mop, direct, loc, nil, 0)
       else begin

cc.notes

@@ -1622,6 +1622,8 @@ If you use #pragma debug 0x0010 to enable stack check debug code, the compiler w
 
 16. When an expression of const- or volatile-qualified struct or union type was passed as a function parameter, incorrect code would be generated.  This could lead to incorrect program behavior or crashes.
 
+17. Incorrect code could sometimes be generated if a long long or unsigned long long value was a non-initial member of a structure, and it was accessed through a pointer to the structure and used as an operand of certain arithmetic, bitwise, or comparison operators.
+
 -- Bugs from C 2.1.1 B3 that have been fixed in C 2.2.0 ---------------------
 
 1.  There were various bugs that could cause incorrect code to be generated in certain cases.  Some of these were specific to certain optimization passes, alone or in combination.