libfsobasics: ReactorChannel: add sysfs capability
libfsobasics: ReactorChannel: add sysfs capability

 * Add rewind option
 * watch PRI in addition to IN

This is needed to watch some sysfs files on the N900,
for example this one:

/sys/devices/platform/gpio-switch/proximity/state

Signed-off-by: Sebastian Reichel <1ea78bda3cb6d36efdb8fc89aad6555e21b4887e@ring0.de>

slyon/debian-fso-deviced,slyon/debian-fso-usaged,slyon/debian-fso-usaged,slyon/debian-libfsoframework,slyon/debian-libfsoframework,slyon/debian-fso-deviced