PowerPC-sysV/eabi, harmonization of section attribute and small data optimization

[David Edelsohn]

	First, I assume that you sent the patch reversed.

	Did you remove the comment about _SDA_BASE_ on purpose?  For what
reason? 

	I understand removing the -G limit in rs6000_encode_section_info
if the section explicitly was selected with the GCC section attribute, but
I think it is incorrect to unilaterally remove the -G limit from
small_data_operand just to allow potentially large objects specified by
the GCC section attribute through -- this will accept any large object
which then will need to be fixed up if it was not suppose to be in the
small data section.

David