Get Irrlicht to compile with IRRLICHT_FAST_MATH on Linux (out-define code which was written for VS and remove #warn which is not a preprocessor command recognized by GCC).
Note that I did this just to do some tests against the fast-math functions - and those tests showed a lot of troubles so I still won't recommend using IRRLICHT_FAST_MATH.


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@4672 dfc29bdd-3216-0410-991c-e03cc46cb475