Compile with -Werror and -Wall (#1116)

* Compile global scheduler with -Werror -Wall.

* Compile plasma manager with -Werror -Wall.

* Compile local scheduler with -Werror -Wall.

* Compile common code with -Werror -Wall.

* Signed/unsigned comparisons.

* More signed/unsigned fixes.

* More signed/unsigned fixes and added extern keyword.

* Fix linting.

* Don't check strict-aliasing because Python.h doesn't pass.

src/common/state/error_table.cc

@@ -1,6 +1,14 @@
 #include "error_table.h"
 #include "redis.h"
 
+const char *error_types[] = {"object_hash_mismatch", "put_reconstruction",
+                             "worker_died"};
+const char *error_messages[] = {
+    "A nondeterministic task was reexecuted.",
+    "An object created by ray.put was evicted and could not be reconstructed. "
+    "The driver may need to be restarted.",
+    "A worker died or was killed while executing a task."};
+
 void push_error(DBHandle *db_handle,
                 DBClientID driver_id,
                 int error_index,