Compiler generates this new instruction for most builtins (with 1-4 arguments.)
Also added new instruction, unikavars(K), to do a sequence of consecutive
uniavar's in one instruction.
asm_inst.P (unikavars(K) and bi_instr)
builtin.H ((is_)builtin_instr) +
builtin.P (many diffs, def of builtin_instr/3)
inprog.H (import is_builtin_instr)
inprog.P (cvt goal to inlinegoal for bi_instrs)
peephole.P (gen unikavars)
tpinline.H (import builtin_instr)
tpinline.P (generate bi_instr instructions)
tprog.H (import warning)
tprog.P (warning and some tbody)