peephole optimizer and code generator bugfixed and improved

Rev: bin/mkpeep.pike:1.3
Rev: src/docode.c:1.13
Rev: src/interpret.c:1.30
Rev: src/language.yacc:1.29
Rev: src/lex.c:1.17
Rev: src/operators.h:1.2
Rev: src/peep.c:1.7
Rev: src/peep.in:1.5
Rev: src/testsuite.in:1.34