re_intuit_start(): reduce use of *_offset macros
There are a number of macros with definitions like
#define anchored_offset substrs->data[0].min_offset
#define float_min_offset substrs->data[1].min_offset
In the two "other substr" branches, replace uses of these macros, e.g.
{
...
foo = prog->float_min_offset;
...
}
with
{
struct reg_substr_datum *other = &prog->substrs->data[other_ix];
...
foo = other->min_offset;
...
}
As well as making debugging easier (a debugger might display real fields
but not macros), and potentially making the binary more compact and faster
(unless the compiler is clever enough to optimise away every use of the
'prog->substrs->data[0]' dereference), it also helps make the two "other
substr" branches more similar, bringing us closer to eventually merging
them.