Blender Git Loki

Include SDL information in system info text.

Adds bpy.app.sdl to expose SDL version information.

When SDL is not available on a Linux system, certain Blender features
are silently disabled (like joystick support in the BGE). This change
is the first step towards making it more obvious why something isn't
working.

SDL information is exposed to Python via bpy.app.sdl, in the same way
as OCIO and OIIO information is exposed.

Generated system-info.txt contains SDL loading method (linked or
dynamically loaded by Blender) and SDL version number.

Reviewed by: sergey, campbellbarton

Differential Revision: https://developer.blender.org/D1112