Explorer++

Patch to handle link to zip files correctly.
If the "handle zip" option is disabled, double-clicking on a link to a zip file will open the zip file as a folder within E++, while double-clicking on the zip file will launch the external zip file handler program.
This patch fixes this problem: double-clicking on a link to the zip file or double-clicking on the zip file will be handled in the same way.
The patch also makes some code improvement to the changes made by patch 19.

NOTE: this patch is against commit 163 + patch 19. The right sequence to apply the patch is:
1) apply patch 19 to commit 163 (http://www.explorerplusplus.com/forum/v ... ?f=7&t=650)
2) apply this patch to the result of 1)

Thanks Michael, I've committed the patch with a few minor changes.