Rename symbol WORDS_BIGENDIAN to DXX_WORDS_BIGENDIAN to show that it is a DXX
symbol, not one inherited from a library.
This is a mostly automated transform, but the changes to SConstruct were
manual.
git grep -wl WORDS_BIGENDIAN -- '*.h' '*.cpp' | xargs sed -i -e 's/^\s*#ifdef \(WORDS_BIGENDIAN\)\>/#if DXX_\1/' -e 's/\s*#\(el\)\?if \(.*\)defined(\(WORDS_BIGENDIAN\))/#\1if \2DXX_\3/' -e 's/^\s*#ifndef \(WORDS_BIGENDIAN\)\>/#if !DXX_\1/'
cd4e5441ba