Add UNUSED_IF_ASSERT_DISABLED and apply it.

Summary:
This replaces (void)x; usages where they x was subsequently
involved in an assertion with this macro to make the
intent more clear.

Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D11451

llvm-svn: 243074
diff --git a/lldb/tools/debugserver/source/DNB.cpp b/lldb/tools/debugserver/source/DNB.cpp
index f630d0b..5462cc4 100644
--- a/lldb/tools/debugserver/source/DNB.cpp
+++ b/lldb/tools/debugserver/source/DNB.cpp
@@ -446,7 +446,7 @@
             else
             {
                 bool res = AddProcessToMap(pid, processSP);
-                (void)res;
+                UNUSED_IF_ASSERT_DISABLED(res);
                 assert(res && "Couldn't add process to map!");
                 return pid;
             }
@@ -495,7 +495,7 @@
         if (pid != INVALID_NUB_PROCESS)
         {
             bool res = AddProcessToMap(pid, processSP);
-            (void)res;
+            UNUSED_IF_ASSERT_DISABLED(res);
             assert(res && "Couldn't add process to map!");
             spawn_waitpid_thread(pid);
         }