Add support for fade duration in the C API

[GoogleCodeExporter]

Hi guys! I'll be reporting a few issues, is this the proper place to report 
them? Is the project still alive, are you guys still fixing bugs or at least 
accepting patches?

Anyway, first issue is (simple enough to fix, too) - the C API has the function 
gme_set_fade( Music_Emu*, int start_msec), and the C++ API has the method 
Music_Emu::set_fade(long start_msec, long length_msec = 8000). The problem is, 
if you're using the C API, you can't set set the fade duration.

So to fix this I suggest adding a function like:

gme_set_fade_with_duration( Music_Emu*, long start_msec, long length_msec );

and adding a few comments in gme.h to explain the difference.

I can provide a patch if someone replies and confirms to me that the project is 
still accepting patches.

Cheers!

Original issue reported on code.google.com by mihai.draghicioiu@gmail.com on 17 Apr 2011 at 1:48

[GoogleCodeExporter]

If I get some time this summer, I may come back to this project. I too have a 
couple of things I'd like to investigate in this library. Mihai, has anyone 
applied your patch?

Original comment by reilith...@gmail.com on 27 Feb 2012 at 5:35

[GoogleCodeExporter]

I dunno, you'd have to check the commits. There were some other patches that 
got accepted into gstreamer 
https://bugzilla.gnome.org/show_bug.cgi?id=647364#c0 but that's all I remember.

Original comment by mihai.draghicioiu@gmail.com on 27 Feb 2012 at 8:35

[GoogleCodeExporter]

If it helps I can accept patches as well, though I've been doing more 
build-system stuff and don't have knowledge of the emulation side of it per se.

I'll be going around today and fixing up issues that are easy so that a 
semi-official 0.6.0 can finally be tagged and released for the benefit of 
packagers everywhere.

Original comment by michael....@gmail.com on 16 Mar 2013 at 9:16