Modules dependencies RE: PATCH: zftp/tcp abstraction

["Andrej Borsenkow" <Andrej.Borsenkow@xxxxxxxxxxxxxx>]

>
> bor@itsrm2% zmodload -u zsh/zftp
> bor@itsrm2% zsh
> bor@itsrm2% zmodload zsh/zftp
> bor@itsrm2% zftp open localhost
> ld.so: zsh: symbol not found: zsh_getipnodebyname
> zsh: killed     zsh
>

Index: Src/Modules/zftp.mdd
+moddeps="zsh/net/tcp"

The problem is, it is currently ignored for modules without auto stuff.
Dependencies are put only in main zsh in Src/bltinmods.list.

To make it work in general every module needs a standard function, let's
call it dep_, that is autogenerated out of moddeps and called before module
is attempted to be loaded to register dependencies. We may need the
counterpart to remove dependencies when module is unloaded (seems
reasonable).

-andrej