Turn on -Wall -Wextra on Mac, and fix all the warnings that crop up for /usr/bin/g++ and Clang 3.3.

bench/PathIterBench.cpp

Index: bench/PathIterBench.cpp
diff --git a/bench/PathIterBench.cpp b/bench/PathIterBench.cpp
index 8bc8add427cd9b9173ed1897df99d2af7b0e29eb..987a752ad96a542d9d0e10479930dfa040d654f7 100644
--- a/bench/PathIterBench.cpp
+++ b/bench/PathIterBench.cpp
@@ -72,7 +72,7 @@ protected:
                 SkPath::Verb verb;
                 SkPoint      pts[4];
 
-                while ((verb = iter.next(pts)) != SkPath::kDone_Verb);
+                while ((verb = iter.next(pts)) != SkPath::kDone_Verb) { }
             }
         } else {
             for (int i = 0; i < N; ++i) {
@@ -80,7 +80,7 @@ protected:
                 SkPath::Verb verb;
                 SkPoint      pts[4];
 
-                while ((verb = iter.next(pts)) != SkPath::kDone_Verb);
+                while ((verb = iter.next(pts)) != SkPath::kDone_Verb) { }
             }
         }
     }