Fix non-inline definition build error with clang++
Fix non-inline definition build error with clang++

Fix the following build error when building with clang++:

    In file included from ../cpp/asyncprogressworker.cpp:13:
    In file included from ../../nan.h:63:
    ../../nan_new.h:207:43: error: inline declaration of 'NanNew' follows non-inline definition
    template <typename T> inline v8::Local<T> NanNew(v8::Handle<T> h);
                                              ^
    ../../nan_implementation_12_inl.h:218:1: note: previous definition is here
    NanNew(v8::Handle<T> h) {
    ^
    In file included from ../cpp/asyncprogressworker.cpp:13:
    In file included from ../../nan.h:63:
    ../../nan_new.h:208:43: error: inline declaration of 'NanNew' follows non-inline definition
    template <typename T> inline v8::Local<T> NanNew(v8::Persistent<T> const& p);
                                              ^
    ../../nan_implementation_12_inl.h:224:1: note: previous definition is here
    NanNew(v8::Persistent<T> const& p) {

g++ is more lenient but clang++ is not wrong to complain.

Fixes: https://github.com/rvagg/nan/issues/231

gagern/nan,saper/nan,lovell/nan,fleg/nan,sanemat/nan,thejinx0r/nan,thefourtheye/nan,evanlucas/nan,gastrodia/nan,mscdex/nan,sesh-kebab/nan,nodejs/nan,saper/nan,lovell/nan,mscdex/nan,eljefedelrodeodeljefe/nan,sanemat/nan,durai145/nan,mscdex/nan,thefourtheye/nan,fleg/nan,lovell/nan,guymguym/nan,addaleax/nan,thejinx0r/nan,sesh-kebab/nan,sesh-kebab/nan,ipmobiletech/nan,ipmobiletech/nan,fleg/nan,LinusU/nan,nodejs/nan,sanemat/nan,thejinx0r/nan,saper/nan,thejinx0r/nan,mikolalysenko/nan,hmalphettes/nan,thefourtheye/nan,eljefedelrodeodeljefe/nan,mikolalysenko/nan,noahjs/nan,durai145/nan,addaleax/nan,LinusU/nan,gagern/nan,guymguym/nan,gastrodia/nan,guymguym/nan,nodejs/nan,gastrodia/nan,Jonekee/nan,Jonekee/nan,saper/nan,Jonekee/nan,evanlucas/nan,durai145/nan,mikolalysenko/nan,LinusU/nan,hmalphettes/nan,ipmobiletech/nan,evanlucas/nan,eljefedelrodeodeljefe/nan,guymguym/nan,ipmobiletech/nan,fleg/nan,thefourtheye/nan,mscdex/nan,gagern/nan,durai145/nan,sesh-kebab/nan,Jonekee/nan,gastrodia/nan,nodejs/nan,LinusU/nan,noahjs/nan,evanlucas/nan,lovell/nan,addaleax/nan,mikolalysenko/nan,sanemat/nan,addaleax/nan,noahjs/nan,noahjs/nan,eljefedelrodeodeljefe/nan,hmalphettes/nan,hmalphettes/nan