Fix warnings from GCC 4.3 about suggested parentheses.

Fix warnings from GCC 4.3 about suggested parentheses.

In GCC 4.3 there are further cases that are suggested to be given
parentheses, to make sure that the result is the actuall behaviour
looked for.

Fix the cases so that warnings are not reported for these.

Signed-off-by: Manuel Nickschas <sputnick@quassel-irc.org>