stlport: Fix strict aliasing violations

This patch fixes strict aliasing violations.
Forward-ported from Chao Yang <chao.yang@linaro.org>'s
patch for 2.3.5.

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
Signed-off-by: zwliew <zhaoweiliew@gmail.com>