autogen.sh: use quoted string variables

Place quotes around the $srcdir, $ORIGDIR and $0 variables to prevent
fall-outs, when they contain space.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>