Implement QUIT logic (poison, medicine etc)

[tgreaves]

Need to implement logic around the QUIT command. Examples: You can't quit when drunk or POISONed in the BBC Micro version.

Relevant BBC BASIC source code lines:

 1640IFC$<>"QUIT"PRINTE$(RND(3)):ENDPROC
 1650IFM>1PRINT"Unable to QUIT while under the influence":VDU7:ENDPROC
 1660IFJPRINT"I need some medical help for the POISON":VDU7:ENDPROC
 1670IFD<6PROCF:!(k+12)=&A01:!(k+8)=Y+1:PROCC(10+RND(E/20),b,"NOSENT")
 1680VDU26,12:IFE>4000 E=4000:PRINT"Aren't you fed up with CAVE?"
 1690PRINT"Hold on";:IFD>=6PROCF