EXTERNALS: Use last version of SoundTailor

New ASSERT macro.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
COMMON: Revert assert as a function - useless!

Assert has to be a preprocessor macro in order to retrieve the original
file/line it was fired from.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>