Changing default of CHECK_FILES to YES

[Thomas Klausner <tk%giga.or.at@localhost>]

Currently, CHECK_FILES defaults to no except if PKG_DEVELOPER is set.
This checks if the installed files and the PLIST match both ways, i.e.
if extra files are installed that are not listed in the PLIST.

I'd like to change this default to yes to make binary packages more
consistent for everyone.

Comments?
 Thomas