When folding a load from a global constant, if the load started in the middle

of an array element (rather than at the beginning of the element) and extended
into the next element, then the load from the second element was being handled
wrong due to incorrect updating of the notion of which byte to load next.  This
fixes PR13442.  Thanks to Chris Smowton for reporting the problem, analyzing it
and providing a fix.

llvm-svn: 160711