Issue 5183 - Provide async interface for FileSystem

libadblockplus.gyp

 {
   'conditions': [[
     # We don't want to use curl on Windows and Android, skip the check there
     'OS=="win" or OS=="android"',
     {
       'variables': {
         'have_curl': 0
       }
     },
     {
@@ skipping 39 matching lines @@
     'xcode_settings':{},
     'include_dirs': [
       'include',
       'third_party/v8/include',
       'third_party/v8',
     ],
     'sources': [
       'include/AdblockPlus/ITimer.h',
       'include/AdblockPlus/IWebRequest.h',
       'include/AdblockPlus/DefaultWebRequest.h',
+      'include/AdblockPlus/IFileSystem.h',
+      'include/AdblockPlus/DefaultFileSystem.h',
       'src/AppInfoJsObject.cpp',
       'src/ConsoleJsObject.cpp',
       'src/DefaultLogSystem.cpp',
       'src/DefaultFileSystem.cpp',
       'src/DefaultTimer.cpp',
       'src/DefaultTimer.h',
       'src/DefaultWebRequest.cpp',
       'src/FileSystemJsObject.cpp',
       'src/FilterEngine.cpp',
       'src/GlobalJsObject.cpp',
@@ skipping 169 matching lines @@
       'test/WebRequest.cpp'
     ],
     'msvs_settings': {
       'VCLinkerTool': {
         'SubSystem': '1',   # Console
         'EntryPointSymbol': 'mainCRTStartup',
       },
     },
   }]
 }