Unify 'ipc.h' and 'ipc_generic.h' across platforms

The distinction between 'ipc.h' and 'ipc_generic.h' is no more. The only
use case for platform-specific extensions of the IPC support was the
marshalling of capabilities. However, this case is accommodated by a
function interface ('_marshal_capability', '_unmarshal_capability'). By
moving the implementation of these functions from the headers into the
respective ipc libraries, we can abandon the platform-specific 'ipc.h'
headers.

qt4/src/lib/qnitpickerviewwidget/qnitpickerviewwidget.cpp

@@ -4,7 +4,7 @@
  * \date   2010-08-26
  */
 
-#include <base/ipc_generic.h>
+#include <base/ipc.h>
 
 #include <string.h>