Suppress statement not reached warnings under Solaris Studio

Suppress statement not reached warnings under Solaris Studio

Solaris Studio issues warnings for statements which can not be reached,
such as statements following an infinite loop.  For example, the return
statement will generate a 'statement not reached' warning in the
following code:

    while (1) {
       /*  no breaks or gotos in this body */
    }
    return 0;

Suppress these warnings by conditionally removing such statements when
building under Solaris Studio.

Change-Id: Ib4f465bf9c00eff0d603e5bd643db7d3a5aa0ba0
Reviewed-on: https://gerrit.openafs.org/12958
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>