Fix minor code issues

ext/gstmoodbar/CMakeLists.txt

@@ -4,6 +4,10 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++11 -U__STRICT_ANSI__ -Wall -Woverloaded-virtual -Wno-sign-compare -fpermissive")
 
+if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wextra -Wimplicit-fallthrough=0 -Wpedantic")
+endif()
+
 include_directories(${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
 
 include_directories(${GLIB_INCLUDE_DIRS})