Fix automagic zlib and jpeg dependencies.

git-svn-id: svn://anonsvn.kde.org/home/kde/trunk/KDE/kdenetwork/krfb/libvncserver@1201534 283d02a7-25f6-0310-bc7c-ecb5cbfe19da

CMakeLists.txt

 project(libvncserver)
 
-find_package(ZLIB)
+macro_optional_find_package(ZLIB)
 macro_log_feature(ZLIB_FOUND "ZLib" "The Zlib compression library" "http://www.zlib.net" FALSE "" "Used by the vncserver library.")
 
-find_package(JPEG)
+macro_optional_find_package(JPEG)
 macro_log_feature(JPEG_FOUND "LibJPEG" "The JPEG library" "" FALSE "" "Used by the vncserver library")
 
 include(CheckIncludeFiles)