slow video since 2.4.2-ac21

[=?iso-8859-2?Q?Jacek_Pop=B3awski?=]

After compiling 2.4.2-ac21 I noticed, that aviplay works much slower than
before. "benchmark" from avifile shows that video output is about 3 times
slower. I tested -ac22, -ac23, ..., -ac27, then 2.4.1, 2.4.2 and few other
versions earlier than -ac21.

2.4.2-ac20
x11perf -putimage100
8000 reps @   0.7736 msec (  1290.0/sec): PutImage 100x100 square

2.4.2-ac27
x11perf -putimage100
3600 reps @   1.3980 msec (   715.0/sec): PutImage 100x100 square

2.2.19 - same result like 2.4.2-ac20

only "-putimage100" shows diffrences, results of "x11perf -scroll100" and
"x11perf -rect100" for all kernel versions were similiar

My hardware: VIA VT82C586B, K6-2, Voodoo3.
My software: XFree86 Version 4.0.99.1 (CVS), glibc-2.1.3, gcc-2.95.3.