Optionally treat BRKs as two-byte instructions

Early data sheets listed BRK as one byte, but RTI after a BRK skips
the following byte, effectively making BRK a 2-byte instruction.
Sometimes, such as when diassembling Apple /// SOS code, it's handy
to treat it that way explicitly.

This change makes two-byte BRKs optional, controlled by a checkbox
in the project settings.  In the system definitions it defaults to
true for Apple ///, false for all others.

ACME doesn't allow BRK to have an arg, and cc65 only allows it for
65816 code (?), so it's emitted as a hex blob for those assemblers.
Anyone wishing to target those assemblers should stick to 1-byte mode.

Extension scripts have to switch between formatting one byte of
inline data and formatting an instruction with a one-byte operand.
A helper function has been added to the plugin Util class.

To get some regression test coverage, 2022-extension-scripts has
been configured to use two-byte BRK.

Also, added/corrected some SOS constants.

See also issue #44.

SourceGen/SGTestData/Expected/2022-extension-scripts_64tass.S

@@ -28,11 +28,9 @@ PrintInlineDciString = $013000
         jsr     L10AB
         jsr     L110F
         jsr     L1108
-        brk
-        .byte   $01
+        brk     #$01
         .word   data01
-        brk
-        .byte   $02
+        brk     #$02
         .word   data02
         rts
 
@@ -80,9 +78,7 @@ L10AB   jsr     PrintInlineNullString
 
 L1108   jsl     PrintInlineL2String
         asl     a
-        brk
-
-        .byte   $60
+        brk     #$60
 
 L110F   jsr     PrintInlineNullString
         adc     $6e

SourceGen/SGTestData/Expected/2022-extension-scripts_Merlin32.S

@@ -21,11 +21,9 @@ PrintInlineDciString equ $013000
          jsr   L10AB
          jsr   L110F
          jsr   L1108
-         brk
-         dfb   $01
+         brk   $01
          dw    data01
-         brk
-         dfb   $02
+         brk   $02
          dw    data02
          rts
 
@@ -71,9 +69,7 @@ L10AB    jsr   PrintInlineNullString
 
 L1108    jsl   PrintInlineL2String
          asl   A
-         brk
-
-         dfb   $60
+         brk   $60
 
 L110F    jsr   PrintInlineNullString
          adc   $6e

SourceGen/SGTestData/Expected/2022-extension-scripts_acme.S

@@ -24,11 +24,9 @@ PrintInlineDciString = $013000
         jsr     L10AB
         jsr     L110F
         jsr     L1108
-        brk
-        !byte   $01
+        !byte   $00,$01
         !word   data01
-        brk
-        !byte   $02
+        !byte   $00,$02
         !word   data02
         rts
 
@@ -76,9 +74,7 @@ L10AB   jsr     PrintInlineNullString
 
 L1108   jsl     PrintInlineL2String
         asl
-        brk
-
-        !byte   $60
+        !byte   $00,$60
 
 L110F   jsr     PrintInlineNullString
         adc     $6e

SourceGen/SGTestData/Expected/2022-extension-scripts_cc65.S

@@ -25,11 +25,9 @@ PrintInlineDciString = $013000
          jsr     L10AB
          jsr     L110F
          jsr     L1108
-         brk
-         .byte   $01
+         .byte   $00,$01
          .word   data01
-         brk
-         .byte   $02
+         .byte   $00,$02
          .word   data02
          rts
 
@@ -81,9 +79,7 @@ L10AB:   jsr     PrintInlineNullString
 
 L1108:   jsl     PrintInlineL2String
          asl     A
-         brk
-
-         .byte   $60
+         .byte   $00,$60
 
 L110F:   jsr     PrintInlineNullString
          adc     $6e