Very minor cleanup to m_getfld() to remove an increment of j.

[nmh] / test / inc / md5sums

4112b1460e11bd94d30944dd464a6662  filler.txt
023aad60eab43f06cf525869a833beb4  fromline.txt
0c4fd7cd528519e83011015bfae3e458  lots_of_headers.txt
34d3e95b7df44d62f685eaf95d823c92  malformed_message.txt
4fda7f16b29d757413cb928d6ffc5aa5  msgheader.txt