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/vty/buffer.c b/src/vty/buffer.c
index a5655b9..e385f9f 100644
--- a/src/vty/buffer.c
+++ b/src/vty/buffer.c
@@ -28,7 +28,7 @@
 #include <stddef.h>
 #include <sys/uio.h>
 
-#include <osmocore/talloc.h>
+#include <osmocom/core/talloc.h>
 #include <osmocom/vty/buffer.h>
 #include <osmocom/vty/vty.h>