net: Skip TestMulticastListener on Solaris

PR go/56172

From Rainer Orth.

R=iant
CC=gofrontend-dev
https://codereview.appspot.com/7305058
libgo: Correct test for whether to use DejaGNU.

R=iant
CC=gofrontend-dev
https://codereview.appspot.com/7299063
crypto/md5: fix for big-endian processors

R=iant
CC=gofrontend-dev
https://codereview.appspot.com/7303060
runtime: Change main in goc2c to return int.

From Uros Bizjak.

R=iant
CC=gofrontend-dev
https://codereview.appspot.com/7300064