* scripttempl/elfppc.sc: Put the PLT between the small and large
BSS segments.
* emulparams/elf32ppc.sh (TEXT_START_ADDR): The ABI says `A
program base of 0x02000000 is recommended...' because otherwise
shared libraries are less efficient. We use 0x01800000 because
otherwise it's impossible to branch to location 0, for instance if
you have an undefined weak symbol.