refactor pollfd related functions into pollfd.c

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8ca29d1..bd052c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -261,6 +261,7 @@
 	lib/handshake.c
 	lib/libwebsockets.c
 	lib/service.c
+	lib/pollfd.c
 	lib/output.c
 	lib/parsers.c
 	lib/context.c