[foreign] NPE when trying to lookup a symbol in the default library when no libraries are loaded

[Jorn Vernee]

> Never mind I found it :)
> 
> void* getDefaultHandle() {
>     // FIXME: This is not yet tested on Windows.
>     return getProcessHandle();
> }

And here's a possible fix [1]

This fixes 2 bugs:

1.) When no library was loaded ClassLoader#NativeLibrary#getFromClass 
threw an NPE (at least on windows). That is fixed by returning 
defaultLibrary.fromClass when the nativeLibraryContext is empty.

2.) The default library search was not working on windows. It was using 
a default handle, which works on unix (dlsym(RTLD_DEFAULT)), but not on 
windows (see https://stackoverflow.com/q/23437007). I have changed the 
implementation from using a default handle to using a new native 
function findEntryInProcess, which does the right thing for Windows 
(iterate over all loaded modules), and does the same thing it used to 
for unix. findEntry is now a Java method, and the original findEntry is 
renamed to findEntry0. The NativeLibrary implementation of findEntry 
forwards to findEntry0, and the anonymous class of the default library 
overrides to forward to findEntryInProcess.

For future reference,
Jorn

[1] : 
https://gist.github.com/JornVernee/7d45780df082cbfb27417b437c7b13a8