• Allow linking webkit pacrunner against javascriptcore-4.0
  (webkit2).
• Allow to disable building of the KDE module (-DWITH_KDE=ON/OFF).
• Fix compilation errors with CLang on MacOSX.
• bindings: perl: Add an option to explicitly link against libperl.so
  Some distributions want to do it, other prefer not to, the library
  is anyway in context of perl.
• config_kde: Add a basic cache and invalidation: performance improvement
  for the KDE module.