Compiling with -fno-common complains as this header's included in multiple
compilation units. In fact, the proper definition of dwarf2_loc_mark_labels
already exists in dwarf2dbg.c, so simply mark this declaration with extern.
Binutils has a "contrib" subdirectory - thus flattening cannot happen
without renaming the upper level contrib directory in a first pass.
Also, don't record this move and remove any keyword expansion.