read.cross for MapQTL format - locus file can't have split lines

[kbroman]

I got an email from a user having trouble reading in data in MapQTL format. It turned out that the locus file had split lines, like this:

P486393_4HS    <nnxnp> {-0}    
nn    np  nn  np  nn  np  nn  np  np  nn
TP511441_4  <nnxnp> {-0}    
nn    np  --  np  nn  nn  nn  nn  np  np

We should be able to handle this, since the number of loci and number of individuals are provided in the file.