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/configure.in b/configure.in
index b572bf4..ead18f0 100644
--- a/configure.in
+++ b/configure.in
@@ -106,8 +106,9 @@
 	include/osmocom/vty/Makefile
 	include/osmocom/codec/Makefile
 	include/osmocom/crypt/Makefile
-	include/osmocore/Makefile
-	include/osmocore/protocol/Makefile
+	include/osmocom/gsm/Makefile
+	include/osmocom/gsm/protocol/Makefile
+	include/osmocom/core/Makefile
 	include/Makefile
 	src/Makefile
 	src/vty/Makefile