Issue 6359 - use C++14 instead of C++1z

meson.build

 project('adblockpluscore', 'cpp', license: ['GPL3'], meson_version: '>0.40.0')
 
 native = get_option('native')
 if native
    target_type='native'
 else
    target_type='js'
 endif
 
 if target_type == 'js'
@@ skipping 22 matching lines @@
   endif
   nodejs = find_program(command.stdout().strip(), 'node', 'nodejs')
 endif
 
 JS_LIBRARY = files(join_paths('compiled', 'library.js'))
 BINDINGS_JS_LIBRARY = files(join_paths('compiled', 'bindings', 'library.js'))
 BINDINGS_GENERATOR = 'bindings.cpp.js'
 BINDINGS_OUTPUT = 'bindings.js'
 COMPILER_OUTPUT = 'compiled.js'
 # params for emcc compilation
-ADDITIONAL_PARAMS = [ '-O3', '-std=c++1z', '-Wall', '-Werror',
+ADDITIONAL_PARAMS = [ '-O3', '-std=c++14', '-Wall', '-Werror',
                       '-fno-rtti' ]
 if target_type == 'js'
 # CXXFLAGS specific to emcc
   ADDITIONAL_PARAMS += [ '-m32', '--memory-init-file', '0',
                          '--emit-symbol-map' ]
 else
   ADDITIONAL_PARAMS += [ '-fsanitize=address' ]
 endif
 # additional params just for core
 CORE_PARAMS = [ '-fno-exceptions' ]
@@ skipping 165 matching lines @@
                          ],
                          cpp_args: GTEST_PARAMS)
   abptest = executable('abptest', test_sources,
                        cpp_args: ADDITIONAL_PARAMS + CORE_PARAMS + ['-DINSIDE_TESTS'],
                        include_directories: include_directories(join_paths(GTEST_DIR, 'include')),
                        link_args: LINK_PARAMS,
                        link_with: [ adblockpluscore, gtest ])
   test('abptest', abptest)
 endif