added more newproc calls in pids.uqb

increases likelihood of contention on each run
move stream functions/data into io.h.cpp

is easier to work with there. also finally renamed core.readline to
be core.getline to match with the underlying c library. and also to
make room for the real readline library
rename addi instruction to be iadd

makes it match with the other arithmetic instructions
also added an arithmetic.uqb test program and updated the documentation