#30 map segfaults if paired end reads are not provided

[Alec Chapman]

the map command will segfault if only one read file is given. Line 556 of match.cc should be:
fp_bfq_r = (optind+3 < argc)? gzopen(argv[optind+3], "r") : 0;
instead of:
fp_bfq_r = (optind < argc)? gzopen(argv[optind+3], "r") : 0;