Always explicitly declare main() with the return type `int'. Don't use

Always explicitly declare main() with the return type `int'. Don't use

* gnome-fileutils.m4: Always explicitly declare main() with the
return type `int'. Don't use exit() since it may be undeclared.
Use `return' instead.
* gnome-pilot.m4: Likewise.
* gperf-check.m4: Likewise.
* linger.m4: Likewise.

svn path=/trunk/; revision=1791