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

Fix various warnings about implicit declarations of functions.
diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index 3f93ffb..f31e3f8 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -46,6 +46,7 @@
 #include <openbsc/transaction.h>
 #include <openbsc/paging.h>
 #include <openbsc/bsc_rll.h>
+#include <openbsc/chan_alloc.h>
 
 #define GSM411_ALLOC_SIZE	1024
 #define GSM411_ALLOC_HEADROOM	128