Generates correct assembly and fix vp8 crash

Properly take the recursive event_sending_lock when looking for listener to
send the event.
Ensure that there will be no event dispatch after vlc_event_detach().

Also, fix a bug in libvlc_event where removing an event handler from an event
callback would lead to a crash.

 * Comment out checks for GL ES, as the plugins are not working.
 * Check libGL only once.
 * Disable EGL by default as it is incomplete and does not correctly
   check for version (1.4 or later is assumed).
 * Only the generic OpenGL output if EGL is available, as there are
   currently no other OpenGL provider plugins.

This reverts commit 07df00dc.

This broke compilation.

This reverts commit 5b859717.

This reverts commit 23e0cb9f.

Some config options do not apply to win32 builds (e.g. QT_NO_ICONV)

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

This keeps windows and mac styles (for mac builds)

Modified-and...
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>