use -Wall -Wextra -Wpedantic when compiling with current gcc versions

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>

cmake/modules/Warnings.cmake

@@ -19,7 +19,7 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
         execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion
                         OUTPUT_VARIABLE GCC_VERSION)
         if(GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8)
-            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wpedantic")
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wpedantic")
         else(GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8)
             set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pedantic")
         endif(GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8)