MinGW support in configure [PATCH]

Hi,

This is a first patch to configure.in adding partial MinGW support to
configure process.

Changelog:

- Added MinGW to platforms needing ENABLE_WIN32SPECIFIC
- Override crypt.h and getopt.h detect on MinGW becasue are provided with
source code
- Override rusage() and getopt() detect on MinGW becasue are emulated in
source code
- Override crypt() and statfs() detect on MinGW becasue are emulated in
source code
- On MinGW inet_ntoa() is not available, so we must use Win32 resolver instead

Regards

Guido

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Guido Serassio
Acme Consulting S.r.l.
Via Gorizia, 69 10136 - Torino - ITALY
Tel. : +39.011.3249426 Fax. : +39.011.3293665
Email: guido.serassio@acmeconsulting.it
WWW: http://www.acmeconsulting.it/