Review raylib_icon resource

- Preparing MP3 files support
- Jumped version to raylib 2.0-dev (too many breaking changes...)

Note that only some lib versions have been updated

Not required any more!

OpenAL Soft backend is still available in audio module, I'm thinking if
exposing it for building in some way or just left it there for advance
users to switch to it manually in case of necessity...

C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin>dumpbin.exe
D:\GitHub\raylib\release\libs\win32\msvc\raylib.dll /DEPENDENTS

Microsoft (R) COFF/PE Dumper Version 14.00.24215.1
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file D:\GitHub\raylib\release\libs\win32\msvc\raylib.dll

File Type: DLL

Image has the following dependencies:

KERNEL32.dll
glfw3.dll
OpenAL32.dll

Summary

4000 .data
1000 .gfids
23000 .rdata
5000 .reloc
1000 .rsrc
68000 .text
1000 _RDATA

Added support for raylib DLL building on MSVC

To be more generic and configurable

mingw32 libraries provided were compiled with a different GCC version
(different computer) and seemed to be incompatible on linkage (missing
symbols).