plus2b.rom: +2B ROM Set. For Spectrum +2A/+2B models

The +2B ROM set includes the following:

ROM 0 - debugged UK 128 editor 
ROM 1 - original 16K BASIC ROM
ROM 2 - RT Russell's BBC BASIC (Z80) ported by JG Harston:

        http://mdfs.net/Software/BBCBasic/Spectrum/

ROM 3 - OpenSE BASIC 3.1.1:

        http://sourceforge.net/projects/sebasic/

The menu options are as follows:

* SE BASIC
  fully debugged, optimized, and enhanced version of Sinclair BASIC

* BBC BASIC
  arguably the best version of classic BASIC with inline Z80 assembler

* 128 BASIC
  fully debugged, new menu system, and virtual numeric keypad support

* 48 BASIC
  the original 1982 ROM, memory paging switched off

* USR 0
  the original 1982 ROM, memory paging enabled
