[Firebird-net-provider] Changes on nant build system of 1.6 version

[<car...@te...>]

Hello:

I have added some changes to the nant build system of the 1.6 sources 
for allow it to run with mono::

I have tested it on windows with mono 0.30 and all builds fine, i will 
try to run some tests with the mono built version later today.






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Best regards

Carlos Guzmán Álvarez
Vigo-Spain