The /src/windows/identity/plugins/common/dynimport.{c,h} files are used

The /src/windows/identity/plugins/common/dynimport.{c,h} files are used
by the NIM Kerberos v5 plug-ins for run-time dynamic linking.  They
currently do not declare or import the following functions:

krb5_get_error_message()
krb5_free_error_message()
krb5_clear_error_message()

This patch adds declarations and definitions required for locating these
functions.  Relies on the addition of these functions to the prototype
list in the Pismere loadfuncs-krb5.h.  See ticket 6045.

ticket: 6046
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20571 dc483132-0cff-0310-8789-dd5450dbe970