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/include/osmocom/gsm/Makefile.am b/include/osmocom/gsm/Makefile.am
new file mode 100644
index 0000000..8685fc9
--- /dev/null
+++ b/include/osmocom/gsm/Makefile.am
@@ -0,0 +1,6 @@
+osmogsm_HEADERS = comp128.h gsm0808.h gsm48_ie.h mncc.h rxlev_stat.h \
+		  gsm0480.h gsm48.h gsm_utils.h rsl.h tlv.h
+
+SUBDIRS = protocol
+
+osmogsmdir = $(includedir)/osmocom/gsm