PowerPC future machine, version 3

[Michael Meissner <meissner at linux dot ibm dot com>]

Since there was a version 2 of one of the previous patches, I'll call this set
version 3.  These patches completely replace the previous patches.

As before, these are for a future PowerPC machine that we are looking at.  If a
real machine is announced that uses these instructions, we may change the name
used in the -mcpu=<machine> option to be the real machine, and drop the
'future' name.

I tried to make the changes suggested in the previous patch set, and keep
things that use the address masks (i.e. RELOAD_REG_*) confined to rs6000.c.

To recap:

    Patch #1:  Basic changes to enable pcrel addresses using PLA/PLD;
    Patch #2:  Optional rework rs6000_setup_reg_addr_mask;
    Patch #3:  Add prefixed RTL support;
    Patch #4:  Add prefixed load/store to all offset instructions;
    Patch #5:  Optionally enable pc-relative on Linux 64-bit ELFv2;
    Patch #6:  Fix a limitation with vector extracts & pcrel addresses;
    Patch #7:  Add PCREL_OPT support;
    Patch #8:  Misc. tests;
    Patch #9:  Prefixed load/store tests with large numeric offsets;
    Patch #10: Pc-relative load/store tests.

I have built each of patches 1-7 in succession, building a bootstrapped
compiler and running make check.  There were no regressions.  I then reran the
tests with patches 8-10 applied, and all of the new patches also pass.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797