readstdin: use getline(3)

readstdin: use getline(3)

currently readstdin():
   - fgets() into a local buffer,
   - strchr() the buffer to eleminate the newline
   - stdups() the buffer into items

a simpler way is to just use getline(3), which will do the allocation
for us; eliminating the need for stdup()-ing.

additionally getline returns back the amount of bytes read, which
eliminates the need for strchr()-ing to find the newline.