Fixed compile errors in VS / gcc for recent commits.

Tested: on Windows & Linux.

Change-Id: I90e18c448fc2fafeb83a6cdc3776174479874562
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ac1c3a6..57fdba0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,13 +52,13 @@
 # source_group(Tests FILES ${FlatBuffers_Tests_SRCS})
 
 if(APPLE)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -stdlib=libc++")
+  set(CMAKE_CXX_FLAGS
+    "${CMAKE_CXX_FLAGS} -std=c++11 -stdlib=libc++ -Wall -pedantic -Werror -Wextra")
 elseif(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
+  set(CMAKE_CXX_FLAGS
+    "${CMAKE_CXX_FLAGS} -std=c++0x -Wall -pedantic -Werror -Wextra")
 endif()
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra")
-
 if(FLATBUFFERS_CODE_COVERAGE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fprofile-arcs -ftest-coverage")
   set(CMAKE_EXE_LINKER_FLAGS