Somebody broke SDL when they updated it. The new version depends on AudioToolbox, so added that as dependency in torque3d.cmake

Engine/lib/sdl/debian/changelog

@@ -1,3 +1,9 @@
+libsdl2 (2.0.4) UNRELEASED; urgency=low
+
+  * Updated SDL to version 2.0.4
+
+ -- Sam Lantinga <slouken@libsdl.org>  Thu, 07 Jan 2016 11:02:39 -0800
+
 libsdl2 (2.0.3) UNRELEASED; urgency=low
 
   * Updated SDL to version 2.0.3

Engine/lib/sdl/debian/copyright

@@ -31,10 +31,6 @@ Copyright: 1995 Erik Corry
            1995 Brown University
 License: BrownUn_UnCalifornia_ErikCorry
 
-Files: src/stdlib/SDL_qsort.c
-Copyright: 1998 Gareth McCaughan
-License: Gareth_McCaughan
-
 Files: src/test/SDL_test_md5.c
 Copyright: 1997-2016 Sam Lantinga <slouken@libsdl.org>
            1990 RSA Data Security, Inc.
@@ -270,13 +266,6 @@ License: BrownUn_UnCalifornia_ErikCorry
   * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
   */
 
-License: Gareth_McCaughan
-  You may use it in anything you like; you may make money
-  out of it; you may distribute it in object form or as
-  part of an executable without including source code;
-  you don't have to credit me. (But it would be nice if
-  you did.)
-
 License: Johnson_M._Hart
   Permission is granted for any and all use providing that this
   copyright is properly acknowledged.

Engine/lib/sdl/debian/libsdl2-dev.install

@@ -5,4 +5,5 @@ usr/lib/*/libSDL2.a
 usr/lib/*/libSDL2main.a
 usr/lib/*/libSDL2_test.a
 usr/lib/*/pkgconfig/sdl2.pc
+usr/lib/*/cmake/SDL2/sdl2-config.cmake
 usr/share/aclocal/sdl2.m4