GCC in RHEL-6 complains about listen:

../../src/conf/domain_conf.c:23718: error: declaration of 'listen' shadows a global declaration [-Wshadow]
/usr/include/sys/socket.h:204: error: shadowed declaration is here [-Wshadow]

This renames all the listen to gListen.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>