Moving some of the BPF filtering code into base class.

This will allow packet sources that don't support BPF natively to
emulate the filtering via libpcap.

src/iosource/CMakeLists.txt

@@ -7,6 +7,7 @@ include_directories(BEFORE
 )
 
 set(iosource_SRCS
+    BPF_Program.cc
     Component.cc
     Manager.cc
     PktDumper.cc