gethostbyname(), etc.  Added a configure test to check for these
libraries.  If they are found, put them in the shell variable
SOCKET_LIBS.  Otherwise, SOCKET_LIBS will be empty.

AC_SUBST the SOCKET_LIBS variable/macro.

ogg123/Makefile.am adds @SOCKET_LIBS@ to the ogg123_LDADD line so that
they will be linked in properly.

svn path=/trunk/vorbis-tools/; revision=1318