Squashed commit of the following:

    arch/mips/src/pic32mz:  Commits the basic architecture port for the PIC32MZEF.
    arch/mips/src/pic32mz:  Begin adding PIC32MZEF files. Initial commit are simply PIC32MZEC files with name changes.
    arch/mips/include/pic32mz:  Add support for the PIC32MZEF family.