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/utils.c b/src/utils.c
index 354fce5..af1829c 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -4,7 +4,7 @@
 #include <errno.h>
 #include <stdio.h>
 
-#include <osmocore/utils.h>
+#include <osmocom/core/utils.h>
 
 static char namebuf[255];
 const char *get_value_string(const struct value_string *vs, uint32_t val)