This patch limits maximum recursion depth for luaL_packsize and luaL_packvalue
functions to 16 nested tables. This check is needed to prevent a crash
on recursive Lua tables.

This patch adds lua_checkfield function - a wrapper for lua_tofield that raises
an error if Lua type can not be converted to lua_field structure. The function
should be used instead of lua_tofield in all bindings where custom types are not
supported.

Also don't call sfree_delayed if snapshot process isn't started, closes #118

#104: -? as --help alias(also for tarancheck), -v -> -V, += number/string in description (need to patch gopt_help += 9 symbols)

Fedora includes debug package by default and will
trigger an error if sees the duplicate.

binutils-devel for build.