Support NNPC and branch instructions ... Outputs to decoder.cc correctly

Support NNPC and branch instructions ... Outputs to decoder.cc correctly

Edits to the CPU model may still need to be made to handle branch likely insts...

arch/isa_parser.py:
    add a NNPC operand ...
arch/mips/isa/base.isa:
    change SPARC to MIPS
arch/mips/isa/decoder.isa:
    typo < to >=
arch/mips/isa/formats/basic.isa:
    spacing
arch/mips/isa/formats/branch.isa:
    add code for branch instructions (still need adjustments for the branch likely)
arch/mips/isa/operands.isa:
    support for NNPC and R31
arch/mips/isa_traits.hh:
    NNPC Addr variable

--HG--
extra : convert_revision : df03d2a71c36dbc00270c2e3d7882b4f09ed97ad