Integer vector check
Examples
bayesfam:::isInt_len(c(1, 2), 2) # should be TRUE
#> [1] TRUE
bayesfam:::isInt_len(1, 2) # should be FALSE, wrong length
#> [1] FALSE
Integer vector check
bayesfam:::isInt_len(c(1, 2), 2) # should be TRUE
#> [1] TRUE
bayesfam:::isInt_len(1, 2) # should be FALSE, wrong length
#> [1] FALSE