[AD] build error in 4.9 svn

[Thomas Fjellstrom <tfjellstrom@xxxxxxxxxx>]

Seems the version of cmake (2.6-patch 0) on my svn server doesn't like this:

if(NOT FLAC_STATIC AND (FLAC_LIBRARY MATCHES "${WIN32_STATIC_LIB_REGEX}"))

it errors out with:

CMake Error: Error in cmake code at
 /root/allegro/allegro-4.9/addons/acodec/CMakeLists.txt:101:
Parse error.  Function missing ending ")".  Instead found left paren with text 
"(".

I'm assuming thats some newer cmake feature, if we do use newer features, we 
should probably tell cmake that we depend on said version of cmake.

-- 
Thomas Fjellstrom
tfjellstrom@xxxxxxxxxx