fix Cocoa build

with change 83940f2, we used LIBS_PRIVATE on the Mac; somewhere
the line where we linked against the Mac libs in the network
kernel was lost.

Reviewed-By: Thiago

Author: Peter Hartmann

src/network/kernel/kernel.pri

@@ -23,7 +23,7 @@ SOURCES += kernel/qauthenticator.cpp \
 unix:SOURCES += kernel/qhostinfo_unix.cpp kernel/qnetworkinterface_unix.cpp
 win32:SOURCES += kernel/qhostinfo_win.cpp kernel/qnetworkinterface_win.cpp
 
-mac:LIBS+= -framework SystemConfiguration
+mac:LIBS+= -framework SystemConfiguration -framework CoreFoundation
 mac:SOURCES += kernel/qnetworkproxy_mac.cpp
 else:win32:SOURCES += kernel/qnetworkproxy_win.cpp
 else:SOURCES += kernel/qnetworkproxy_generic.cpp