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/crc16.c b/src/crc16.c
index 8ac8031..3a0d0dd 100644
--- a/src/crc16.c
+++ b/src/crc16.c
@@ -8,7 +8,7 @@
  * Version 2. See the file COPYING for more details.
  */
 
-#include <osmocore/crc16.h>
+#include <osmocom/core/crc16.h>
 
 /** CRC table for the CRC-16. The poly is 0x8005 (x^16 + x^15 + x^2 + 1) */
 uint16_t const crc16_table[256] = {