Fix the build break on Ubuntu 15.10 when gcc 5.2.1 is used

Summary:
Using gcc 5.2.1 to compile RocksDB on Ubuntu 15.10 results in a warning about unused variable. Warning is treated as an error and all of it results in a build break. Fix the issue and make sure that everything compiles with that particular configuration.

P.S. Lint complains about a non-ASCII character used in the source code ("Wagner-Fischer"). Fix this as well.

Test Plan:
  # Everything compiler cleanly on the system which exhibited the problem.
  # `make clean && make -j 16` on CentOS.
  # `make clean && USE_CLANG=1 make -j 16` on CentOS.

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55503

third-party/gtest-1.7.0/fused-src/gtest/gtest.h

@@ -7682,7 +7682,7 @@ namespace edit_distance {
 // Returns the optimal edits to go from 'left' to 'right'.
 // All edits cost the same, with replace having lower priority than
 // add/remove.
-// Simple implementation of the Wagner–Fischer algorithm.
+// Simple implementation of the Wagner-Fischer algorithm.
 // See http://en.wikipedia.org/wiki/Wagner-Fischer_algorithm
 enum EditType { kMatch, kAdd, kRemove, kReplace };
 GTEST_API_ std::vector<EditType> CalculateOptimalEdits(
@@ -17586,7 +17586,7 @@ internal::CartesianProductHolder10<Generator1, Generator2, Generator3,
                       GTEST_TEST_CLASS_NAME_(test_case_name, test_name)>()); \
       return 0; \
     } \
-    static int gtest_registering_dummy_; \
+    static int gtest_registering_dummy_ GTEST_ATTRIBUTE_UNUSED_; \
     GTEST_DISALLOW_COPY_AND_ASSIGN_(\
         GTEST_TEST_CLASS_NAME_(test_case_name, test_name)); \
   }; \