[PATCH V5] include: Add xact3.h

[Vijay Kiran Kamuju]

Based on work by Ethan Lee and Alistair Leslie-Hughes
Use the header file directly instead of idl file just like other
directx headers like dsound.h
Implementing idl file involves a lot of hacks.

V2:
Fix overflow warnings and typos

V3:
Correct IXACT3SoundBank interface

V4:
Correct IXACT3WaveBank, IXACT3Engine interface

V5:
use INT_MAX, INT_MIN instead of LONG_MAX, LONG_MIN constants

Signed-off-by: Vijay Kiran Kamuju <infyquest(a)gmail.com>