Fix SEGV in ped_to_bed_multichar_allele: accept multichar-long tri/quad-...

* When .ped file contains multichar tri/quad-allelic variant, `--make-bed` causes SEGV.
* Added `map_is_unsorted` flag appropriately.

#### sample_input.ped
```
1 1000000000 0 0 1 1 A A T T
1 1000000001 0 0 1 2 T T GG G
```