int(X..Y) implemented, plus some bugfixes and removed two memory 'leaks'

Rev: src/constants.c:1.15
Rev: src/global.h:1.28
Rev: src/interpret.c:1.116
Rev: src/interpret.h:1.27
Rev: src/language.yacc:1.111
Rev: src/las.c:1.75
Rev: src/main.c:1.64
Rev: src/modules/Gmp/mpz_glue.c:1.40
Rev: src/operators.c:1.48
Rev: src/pike_types.c:1.54
Rev: src/pike_types.h:1.18
Rev: src/stralloc.h:1.33
Rev: src/svalue.h:1.22
Rev: src/testsuite.in:1.151