misc: Add prototypes to header files, include more header files

Fix various warnings about implicit declarations of functions.
diff --git a/openbsc/src/e1_config.c b/openbsc/src/e1_config.c
index e743132..4a1cbb0 100644
--- a/openbsc/src/e1_config.c
+++ b/openbsc/src/e1_config.c
@@ -8,6 +8,7 @@
 #include <openbsc/trau_frame.h>
 #include <openbsc/trau_mux.h>
 #include <openbsc/misdn.h>
+#include <openbsc/ipaccess.h>
 #include <openbsc/talloc.h>
 
 #define SAPI_L2ML	0