standard places ("/etc/objformat", ${OBJFORMAT}, argv) for an
indication of the user's preferred object file format. This
consolidates some code that was starting to be duplicated in more
and more places.
Use the new function in ldconfig.
Note: I don't think that gcc should use getobjformat(), even though
it could. The compiler should limit itself to functions that are
widespread, to ease porting and cross-compilation.
