add dedicated 8bit low register accessor

git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@11983 6c8e4198-a580-4521-a02f-c9ae86df1db9
make use of new accessor

git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@11984 6c8e4198-a580-4521-a02f-c9ae86df1db9