Windows dllexport issue in apr-util 1.6.0 + fix

[Brecht Sanders]

Hi

In apr-util 1.6.0 there are dllexport issues when building on Windows
(in my case using MinGW-w64).

These issues can be fixed by replacing APR_DECLARE with APU_DECLARE in
the following files:

    include/apr_crypto.h
    crypto/apr_crypto.c
    include/apr_siphash.h
    crypto/apr_siphash.c

and include apu.h where needed.

Regards

  Brecht Sanders