Use inotify instead of polling on Linux.

This should solve problems people are seeing when a file changes
twice within a second and thus is missed for polling.

bld/Android.mk

@@ -10,7 +10,7 @@ LOCAL_SRC_FILES :=  bpf.c cache.c dbus.c dhcp.c dnsmasq.c \
 		    dhcp6.c rfc3315.c dhcp-common.c outpacket.c \
 		    radv.c slaac.c auth.c ipset.c domain.c \
 	            dnssec.c dnssec-openssl.c blockdata.c tables.c \
-		    loop.c
+		    loop.c inotify.c
 
 LOCAL_MODULE := dnsmasq