Added several linux improvements to the event loop, MIDI and X11 (see commit messsage)

MIDI: Several ALSA Seq improvements
===================================

Many things were done in this patch (I couldn't really split in several
patches):
 * Only one ALSA Sequencer client per application
 * ALSA Sequencer client name is the application's name by default
 * Fixed a bug when getDeivces() would return devices created by the
   application itself
 * Only ports created with createNewDevice() are allowed to be subscribed,
   other ports (created by openDevice()) doesn't allow subscription
 * AlsaPort is now handled by AlsaClient, basically having the proper
 representation such as the ALSA Sequencer has.

Files: Fix default directory paths
==================================

Some information on:
* Linux LSB FHS:
  http://www.linuxfoundation.org/collaborate/workgroups/lsb/fhs-30
* https://wiki.archlinux.org/index.php/Xdg_user_directories

Refactor Event loop to remove X11 dependency
============================================

The goal of this refactor was to remove X11 dependencies on juce_events
to enable non-gui applications (example, Embedded Linux apps) to have no
libx11 dependency.

The side-effect of this refactor is easy implementation of other Linux
graphical back-end, cleanup some code, better handling of X displays and
other benefits.

I removed a lot of the code from juce_linux_Windowing to separate files
for clarity. I also renamed all Linux X11 files to *linux_X11* instead of
just *linux*.

X11: Remove unnecessary XGrabButton call
========================================

This call is made unnecessary if used proper window flags when a window
is created.

modules/juce_opengl/juce_opengl.cpp

@@ -208,7 +208,7 @@ private:
  #include "native/juce_OpenGL_win32.h"
 
 #elif JUCE_LINUX
- #include "native/juce_OpenGL_linux.h"
+ #include "native/juce_OpenGL_linux_X11.h"
 
 #elif JUCE_ANDROID
  #include "native/juce_OpenGL_android.h"