Add CMake build files

src/network/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_library(net OBJECT network.c net_pcap.c net_slirp.c net_dp8390.c net_3c503.c
+	net_ne2000.c net_pcnet.c net_wd8003.c net_plip.c)
+
+add_subdirectory(slirp)
+target_link_libraries(86Box slirp)

src/network/slirp/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_library(slirp STATIC arp_table.c bootp.c cksum.c dnssearch.c if.c ip_icmp.c
+	ip_input.c ip_output.c mbuf.c misc.c sbuf.c slirp.c socket.c tcp_input.c
+	tcp_output.c tcp_subr.c tcp_timer.c udp.c util.c version.c)
+
+target_link_libraries(slirp wsock32 iphlpapi)