include: reorganize headers file to include/osmocom/[gsm|core]

This patch moves all GSM-specific definitions to include/osmocom/gsm.
Moreover, the headers in include/osmocore/ have been moved to
include/osmocom/core.

This has been proposed by Harald Welte and Sylvain Munaunt.

Tested with `make distcheck'.

Signed-off-by: Pablo Neira Ayuso <pablo@gnumonks.org>
diff --git a/src/statistics.c b/src/statistics.c
index 34e6a40..183005d 100644
--- a/src/statistics.c
+++ b/src/statistics.c
@@ -23,9 +23,9 @@
 
 #include <sys/types.h>
 
-#include <osmocore/linuxlist.h>
-#include <osmocore/talloc.h>
-#include <osmocore/statistics.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/statistics.h>
 
 static LLIST_HEAD(counters);