[AD] Fix for the test program

[Eric Botcazou <ebotcazou@xxxxxxxxxx>]

While privately discussing whether to force function inlining with Bob, I 
discovered that the test program doesn't really time the fixed math 
functions as advertised, since the calls are optimized away both by gcc 
2.95.3 and gcc 3.2.x !

Fixed thusly on trunk and branch.

-- 
Eric Botcazou

--- /home/eric/cvs/allegro/tests/test.c	Sat Oct  5 08:40:17 2002
+++ allegro/tests/test.c	Mon Feb 17 10:50:04 2003
@@ -1433,7 +1433,7 @@
 void misc(void)
 {
    BITMAP *p;
-   fixed x, y, z;
+   volatile fixed x, y, z;
 
    clear_to_color(screen, palette_color[0]);
    textout_ex(screen,font,"Timing some other routines...", xoff+44, 6, palette_color[15], palette_color[0]);