import the -current GCC 4.5 sources as gcc.old in preparation for
upgrading the normal GCC to 4.8.

this tree has had ChangeLog entries removed, as well as all the
other components we delete, and "only" weighs in around 140MB now.
update gcc.old from GCC 4.5 versions that build with EXTERNAL_GCC_SUBDIR,
should be identicaly for the 'dist' subdir.
re-import GCC 4.5* with latest fixes to build as gcc.old.
should be the last time we need to do this.