[krbdev.mit.edu #6504] Create Cygwin archives for KfW libraries

[asanka@mit.edu via RT]

Applications that are compiled under the Cygwin environment can't link
directly with the import libraries (.lib) included in the KfW SDK.  Such
applications need to be linked against corresponding Cygwin import
libraries (.a).

This patch contains modifications to the build system and the WiX
installer to generate and distribute Cygwin import libraries that
correspond to the core KfW DLLs.

The patch was created against the 1.6 branch.