Switch to using memcpy to avoid strict aliasing rule errors in GCC 4.4

I am not 100% sure that this won't break anything, but it does appear to solve the strict aliasing errors I was getting, e.g.:

cc1: warnings being treated as errors
/home/dfj/software/obix/src/adaptors/bms_adaptor.c: In function ‘bms_setup_hvsb_hist’:
/home/dfj/software/obix/src/adaptors/bms_adaptor.c:701: error: dereferencing pointer ‘val.31’ does break strict-aliasing rules
/home/dfj/software/obix/src/adaptors/bms_adaptor.c:701: error: dereferencing pointer ‘val.31’ does break strict-aliasing rules
/home/dfj/software/obix/src/adaptors/bms_adaptor.c:701: note: initialized from here