next round of MIPS ISA changes

next round of MIPS ISA changes

src/arch/mips/isa/decoder.isa:
    div,divu,ext,seb,seh, fp conditonal moves, fp indexed memory...
src/arch/mips/isa/formats/mem.isa:
    MemoryNoDisp class .. use sext<> function instead of doing it manually
src/arch/mips/regfile/float_regfile.hh:
    use bits function

--HG--
extra : convert_revision : cbbda9499185b91bdb2a6198fe1b961be04f9265