VTY: implement talloc context introspection command

This change introduces a new command, which could be used to
inspect the application's talloc context directly from VTY.
To enable this feature, an application need to provide it's
context via the 'vty_app_info' struct, and register the VTY
command by calling the osmo_talloc_vty_add_cmds().

The new command is a sub-command of 'show':

  show talloc-context <context> <depth> [filter]

Currently the following contexts may be inspected:

  - application - a context provided by an application;
  - null - all contexts, if NULL-context tracking is enabled.

A report depth is defined by the next parameter, and could be:

  - full - full tree report, as the talloc_report_full() does;
  - brief - brief tree report, as the talloc_report() does;
  - DEPTH - user defined maximal report depth.

Also, there are two optional report filters:

  - regexp - print only contexts, matching a regular expression;
  - tree - print a specific context, pointed by specified address.

The command output is formatted the same way as in case of calling
the talloc_report() or talloc_report_full().

Change-Id: I43fc42880b22294d83c565ae600ac65e4f38b30d
diff --git a/src/vty/Makefile.am b/src/vty/Makefile.am
index e083a1c..1dc76c3 100644
--- a/src/vty/Makefile.am
+++ b/src/vty/Makefile.am
@@ -10,7 +10,8 @@
 lib_LTLIBRARIES = libosmovty.la
 
 libosmovty_la_SOURCES = buffer.c command.c vty.c vector.c utils.c \
-			telnet_interface.c logging_vty.c stats_vty.c fsm_vty.c
+			telnet_interface.c logging_vty.c stats_vty.c \
+			fsm_vty.c talloc_ctx_vty.c
 libosmovty_la_LDFLAGS = -version-info $(LIBVERSION) -no-undefined $(TALLOC_LIBS)
 libosmovty_la_LIBADD = $(top_builddir)/src/libosmocore.la
 endif