Fix infinite loops and crashes related to unreachable blocks and SSE/MMX instructions and registers.

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Add USE/DEF of ESI to interrupt calls; eliminate duplicate PTRIMMED annotations for lea instructions.

Initialize Region in InstAccess constructor; don't discard stack referents with allocation address 0 (environment data).

Make add-with-carry and sub-with-borrow usually like add and sub, but with the possibility of changing the register type from POINTER to NUMERIC.

Continue building infrastructure to propagate memory DEFs until indirect writes create possible alias problems.