[NOT READY] fix some linux compile issues with CEF 2171

This PR fixes some compile issues, but I'm still seeing errors that I haven't been able to resolve:

```
jasonsj@ubuntu:~/Github/brackets-shell$ grunt build
Running "build" task

Running "build-linux" task
>> out/Release/obj.target/Brackets/appshell/cefclient_gtk.o: In function `main':
>> cefclient_gtk.cpp:(.text+0x7cc): undefined reference to `CefExecuteProcess(CefMainArgs const&, CefRefPtr<CefApp>, void*)'
>> cefclient_gtk.cpp:(.text+0xb99): undefined reference to `CefInitialize(CefMainArgs const&, CefStructBase<CefSettingsTraits> const&, CefRefPtr<CefApp>, void*)'
>> cefclient_gtk.cpp:(.text+0xff1): undefined reference to `CefBrowserHost::CreateBrowser(CefWindowInfo const&, CefRefPtr<CefClient>, CefStringBase<CefStringTraitsUTF16> const&, CefStructBase<CefBrowserSettingsTraits> const&, CefRefPtr<CefRequestContext>)'
>> out/Release/obj.target/libcef_dll_wrapper/libcef_dll/wrapper/libcef_dll_wrapper.o: In function `CefShutdown()':
>> libcef_dll_wrapper.cc:(.text+0x2ac): undefined reference to `CefCppToC<CefCompletionHandlerCppToC, CefCompletionHandler, _cef_completion_handler_t>::DebugObjCt'
>> libcef_dll_wrapper.cc:(.text+0x365): undefined reference to `CefCToCpp<CefDOMEventCToCpp, CefDOMEvent, _cef_domevent_t>::DebugObjCt'
>> libcef_dll_wrapper.cc:(.text+0x38a): undefined reference to `CefCppToC<CefDOMEventListenerCppToC, CefDOMEventListener, _cef_domevent_listener_t>::DebugObjCt'
>> libcef_dll_wrapper.cc:(.text+0x952): undefined reference to `CefCppToC<CefTraceClientCppToC, CefTraceClient, _cef_trace_client_t>::DebugObjCt'
>> out/Release/obj.target/libcef_dll_wrapper/libcef_dll/wrapper/libcef_dll_wrapper.o: In function `CefGetTraceBufferPercentFullAsync()':
>> libcef_dll_wrapper.cc:(.text+0x12a9): undefined reference to `cef_get_trace_buffer_percent_full_async'
>> out/Release/obj.target/libcef_dll_wrapper/libcef_dll/wrapper/libcef_dll_wrapper.o: In function `CefEndTracingAsync()':
>> libcef_dll_wrapper.cc:(.text+0x12c2): undefined reference to `cef_end_tracing_async'
>> out/Release/obj.target/libcef_dll_wrapper/libcef_dll/wrapper/libcef_dll_wrapper.o: In function `CefCppToC<CefTraceClientCppToC, CefTraceClient, _cef_trace_client_t>::Wrap(CefRefPtr<CefTraceClient>)':
>> libcef_dll_wrapper.cc:(.text._ZN9CefCppToCI20CefTraceClientCppToC14CefTraceClient19_cef_trace_client_tE4WrapE9CefRefPtrIS1_E[_ZN9CefCppToCI20CefTraceClientCppToC14CefTraceClient19_cef_trace_client_tE4WrapE9CefRefPtrIS1_E]+0x4f): undefined reference to `CefTraceClientCppToC::CefTraceClientCppToC(CefTraceClient*)'
>> out/Release/obj.target/libcef_dll_wrapper/libcef_dll/ctocpp/domnode_ctocpp.o: In function `CefCppToC<CefDOMEventListenerCppToC, CefDOMEventListener, _cef_domevent_listener_t>::Wrap(CefRefPtr<CefDOMEventListener>)':
>> domnode_ctocpp.cc:(.text._ZN9CefCppToCI25CefDOMEventListenerCppToC19CefDOMEventListener24_cef_domevent_listener_tE4WrapE9CefRefPtrIS1_E[_ZN9CefCppToCI25CefDOMEventListenerCppToC19CefDOMEventListener24_cef_domevent_listener_tE4WrapE9CefRefPtrIS1_E]+0x4f): undefined reference to `CefDOMEventListenerCppToC::CefDOMEventListenerCppToC(CefDOMEventListener*)'
>> collect2: error: ld returned 1 exit status
>> make: * [out/Release/Brackets] Error 1
Warning: Task "build-linux" failed. Use --force to continue.

Aborted due to warnings.

```