Windows support, performance, passthrough mode

[giachello]

Hi there. I made several changes to your code.

• Added support for Windows, compiled under cygwin (including transparent support for \r\n newlines)
• Fixed automake script to work on Windows
• Improved performance of the mbox code by 25% by using larger memory buffers and fewer realloc/strcpy
• Support for passthrough mode which allows to save the matched messages to a file and pipe to std the rest, allowing effectively to split the mbox into two
• Execution status indicator which can be helpful for large files Tried this on 10+GB large mbox files from GMAIL and works pretty fine.

[dspiljar]

Hi Giovanni,

Many thanks for this pull request, quite amazing stuff! I will edit it before merging, however, because I am reluctant about the end-of-line sequence question, as explained here.

Best regards, Daniel

[dspiljar]

Hi Giovanni,

Would you be so kind and split this pull request into multiple separate ones, perhaps according to your points above, just for the sake of clarity in the commit log?

It looks good and I am ready to merge most of it, with the exception of the \r\n end-of-line sequence question, which needs a more elaborated solution (as discussed).

Thanks!

Best regards, Daniel