binutils: Makefile and Config.in rework for oprofile ext toolchain compilation

  * When select full binutils binaries use the default INSTALL_TARGET_CMDS
    from AUTOTARGET.
  * Menu config improvement.
  * Install libiberty into Staging dir.

[Peter: Fix typos, Config.in fixes, install libiberty to target as well]
Signed-off-by: Benoit Mauduit <benoit.mauduit@openwide.fr>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>