Hi guix,

While test-driving vlc on my laptop, I notice our vlc isn't build with
subtitle support. So, I go ahead and add as many inputs as possible.

There are 3 points to pay attention:
1. Add liba52 as input and remove the old FIXME
2. Add a new FIXME since gnome-vfs is not detected by the vlc build system
3. Our vlc was built with fast-math disabled as explained in the
comment. However, this is actually not necessary, vlc would built with
'-ffast-math -fno-finite-math-only'.