Branch: b1_4

Branch: b1_4
For some reason having an inline ll_set_rdonly() with HAVE_OLD_DEV_SET_RDONLY
is causing gcc to miscompile and way overstep the array bounds (2 == 1792
in some cases it seems).  Move this code to a function.

Add some more 64-bit sanity checks (it was do_div() on BGL that broke things
previously).