stats/vty: Add stats_vty.c

This file will contain the VTY code related to statistics.

This commit adds a minimal file with just as single VTY command:

- show stats    This command shows all statistical values

To enable this and future commands, the main program needs to call
stats_vty_add_cmds().

Sponsored-by: On-Waves ehf
diff --git a/include/Makefile.am b/include/Makefile.am
index 7f8dd77..af189c3 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -113,6 +113,7 @@
                           osmocom/vty/buffer.h \
                           osmocom/vty/command.h \
                           osmocom/vty/logging.h \
+                          osmocom/vty/stats.h \
                           osmocom/vty/misc.h \
                           osmocom/vty/telnet_interface.h \
                           osmocom/vty/vector.h \