Detect more benign truncations in IDIOM 2 based on the original source of the truncated operand and its subsequent uses.

Improved detection of truncation idiom 14 and overflow idiom 10 (multiplication by large constant), including fixing IDA Pro operands list for imul opcode.

Benign underflow idioms 11 and 12; subtrahend is large constant, or both operands were obtained from zero-extended moves.

Build RTLs for dryrun lib opcodes; fix uninit vars and clean up code; start mul by large const idiom recognition.

Infer signedness from opcodes; suppress overflow and underflow checks on small values from condition codes.