cygwin ld import library issue fix (removing unused "_nm_" symbols)

[Ralf Habacker]

> In theory, it looks good. However, have you tested the following:
>
> a) build a dll using an unmodified ld.
> b) build an app that uses that dll, and which accesses both a function
> export and a data export from the dll.
> c) rebuild the dll using your modified ld.
> d) does the app still work, without relinking?

Because the patch does only affect generating import library, this condition is
obsolate.

A real test is relinking the app with an unmodified ld. I'll send a testcase
protocol in the near furture.


Regards
Ralf