RFA: Add range checking to initialisation of special entries in ggc-page's size_lookup table

[Nick Clifton]

Hi Ian,

> This is OK with the change from "break" to "continue" that Richard
> pointed out.  Assuming it has been bootstrapped and tested, of
> course--you didn't mention.

Because, in my infinite stupidity I forgot to run those tests.  I have 
now done so, the bootstrap worked and there were no regressions in the 
gcc testsuite, so I have checked the (updated) patch in.

Cheers
   Nick