src: use include/osmocom/abis instead of include/osmocom/gsm/abis

Harald prefers short paths.

This patch also remove commented includes in several files.
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index 9894920..40d69b6 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -39,18 +39,9 @@
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/logging.h>
 #include <talloc.h>
-#include <osmocom/gsm/abis/e1_input.h>
-#include <osmocom/gsm/abis/ipaccess.h>
+#include <osmocom/abis/e1_input.h>
+#include <osmocom/abis/ipaccess.h>
 #include <osmocom/core/socket.h>
-/*#include <openbsc/debug.h>
-#include <openbsc/gsm_data.h>
-#include <openbsc/abis_nm.h>
-#include <openbsc/abis_rsl.h>
-#include <openbsc/subchan_demux.h>
-#include <openbsc/e1_input.h>
-#include <openbsc/ipaccess.h>
-#include <openbsc/socket.h>
-#include <openbsc/signal.h> */
 
 #define PRIV_OML 1
 #define PRIV_RSL 2