updating GCC and gmp/mpc/mpfr

[matthew green <mrg%eterna.com.au@localhost>]

hi folks.


you've probably seen the move from gcc to gcc.old for our 5.4 tree.
before i get gcc 6.4 imported in gcc, i want to update the gmp,m pc
and mpfr trees as well.  this is non trivial, and is independant of
gcc itself.  as they're fairly complex components needing porting
to each cpu, i'm going to put the current ones in to a .old subdir
and use those optionally in gcc and gcc.old.  my plan is to enable
their update to happen separately and before updating gcc 6 itself,
allowing more parallelism in this effort.

if you have any major concerns about this approach, please speak up.

thanks.


.mrg.