[ODE] gcc 3.x optimization fix

[Allen Bierbaum]

I was just looking at the optimizations used for ode when building with 
gcc on Linux and I noticed the comment in Makefile about problems with 
Opcode at -O2 level.  I ran into similar problems using Opcode and was 
able to track it down to being some type of aliasing issue (probably 
because of all the static casting going on behind the scenes).  I was 
able to fix the problem by adding "-fno-strict-aliasing" to the build 
line.  (my full build like used "-O3 -ffast-math -fno-strict-aliasing").

Hopefully this can help to fix the problems people see with ODE at high 
optimization levels.

-Allen