Interrupt system implemented, some new programs.

Programs/testPrograms/faultResumeTest.asm

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+; Tests a fault handler that steps over the byte it could not decode and carries on.
+;
+; The frame holds the address of the offending byte rather than the one after it, so a
+; handler can see exactly what failed. The cost is that returning with a bare RETI meets
+; the same byte again, which is why this handler moves the saved address on by one
+; first. MVSD is what lets it reach the frame at all.
+;
+; 0xFE is not an instruction. Writing it as a literal is the only way past the
+; assembler, which is what makes a program containing one buildable.
+;
+; Correct output is:
+;   O         printed before the byte that fails
+;   K         printed after the handler stepped over it
+
+#Program
+
+start:
+  INIA 0d79         ; 'O'
+  OUTA 0x00
+  INIA 0x0A
+  OUTA 0x00
+
+  0xFE              ; Not an instruction. The handler steps over this.
+
+  INIA 0d75         ; 'K'. Reached only because the handler moved the address on.
+  OUTA 0x00
+  INIA 0x0A
+  OUTA 0x00
+  HALT
+
+faultHandler:
+  ; The frame sits above the Stack Pointer, which points at the next free slot. The
+  ; address to resume at went on first, so it is furthest up: high byte 13 above the
+  ; Stack Pointer, low byte 14 above.
+  MVSD.0
+  DPUP.0 0d14
+  LDA.0
+  INCA              ; Step past the one byte that failed.
+  STA.0
+  BRC carried       ; The low byte wrapped, so the high byte needs the carry.
+  RETI
+
+carried:
+  DPDN.0 0d01
+  LDA.0
+  INCA
+  STA.0
+  RETI
+
+#Vectors
+
+  BadOpcode  faultHandler