Add extra parentheses to macro bodies

Add extra parentheses to macro bodies

In order to avoid surprises due to operator precedence, the bodies
of macros that are intended to be used as values should always
be enclosed in an outer set of parentheses, if they contain more than
one term.

Change-Id: If175b1977b9452a7507c5906e4e611eccafb4d67
Reviewed-on: https://gerrit.openafs.org/12143
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>