Sound effect constants

The following sound effect constants exists:
 * se_none
 * se_chorus
 * se_echo
 * se_flanger
 * se_gargle
 * se_reverb
 * se_compressor
 * se_equalizer

They are used in calls to the function sound_effect_set(snd,effect) You can set a combination of effects by adding up the values. So e.g. you can use sound_effect_set(snd,se_echo+se_reverb); to get a combination of echo and reverb effects.