Separate BBC BASIC ROM from the Electron.

Machines/Utility/ROMCatalogue.cpp

@@ -71,6 +71,18 @@ const std::vector<Description> &Description::all_roms() {
 			0x00c7a3d3u
 		},
 
+	//
+	// Acorn 8-bit.
+	//
+		{
+			AcornBASICII,
+			"Acorn",
+			"the Acorn BASIC II ROM",
+			Files{"basic.rom", "basic2.rom"},
+			16_kb,
+			0x79434781u
+		},
+
 	//
 	// Acorn Electron.
 	//

Machines/Utility/ROMCatalogue.hpp

@@ -28,8 +28,10 @@ enum Name {
 	AcornRISCOS311,
 	AcornRISCOS319,
 
-	// Acorn Electron.
+	// Acorn 8-bit.
 	AcornBASICII,
+
+	// Acorn Electron.
 	AcornElectronMOS100,
 	PRESADFSSlot1,
 	PRESADFSSlot2,

ROMImages/Acorn/readme.txt

@@ -0,0 +1,5 @@
+ROM files would ordinarily go here; the copyright status of these is uncertain so they have not been included in this repository.
+
+Expected files:
+
+basic.rom

ROMImages/BBCMicro/readme.txt

@@ -2,5 +2,4 @@ ROM files would ordinarily go here; the copyright status of these is uncertain s
 
 Expected files:
 
-basic2.rom
 os12.rom