Fix a linker error on GNU Hurd.

gcc  -shared libpcap.so.$MAJOR_VER \
   -o libpcap.so.$VER pcap-hurd.o fad-getad.o  pcap-dbus.o  pcap.o
 gencode.o optimize.o nametoaddr.o etherent.o fmtutils.o savefile.o
 sf-pcap.o sf-pcapng.o pcap-common.o bpf_image.o bpf_filter.o bpf_dump.o
 scanner.o grammar.o strlcat.o strlcpy.o  -lrt -ldbus-1
/usr/bin/ld: cannot find libpcap.so.1: No such file or directory

Author: sthibaul

aclocal.m4

@@ -469,7 +469,7 @@ AC_DEFUN(AC_LBL_SHLIBS_INIT,
 	    aix*)
 		    ;;
 
-	    freebsd*|netbsd*|openbsd*|dragonfly*|linux*|osf*|haiku*|midipix*)
+	    freebsd*|netbsd*|openbsd*|dragonfly*|linux*|osf*|haiku*|midipix*|gnu*)
 		    #
 		    # Platforms where the linker is the GNU linker
 		    # or accepts command-line arguments like

configure

@@ -5239,7 +5239,7 @@ $as_echo "#define const /**/" >>confdefs.h
 	    aix*)
 		    ;;
 
-	    freebsd*|netbsd*|openbsd*|dragonfly*|linux*|osf*|haiku*|midipix*)
+	    freebsd*|netbsd*|openbsd*|dragonfly*|linux*|osf*|haiku*|midipix*|gnu*)
 		    #
 		    # Platforms where the linker is the GNU linker
 		    # or accepts command-line arguments like