qsysteminfo_linux.cpp and qpulseaudioengine.cpp missing unistd.h

Compiling with gcc 4.7 fails with the following error:

linux/qsysteminfo_linux.cpp: In member function 'bool QtMobility::QSystemScreenSaverPrivate::setScreenSaverInhibit()':
linux/qsysteminfo_linux.cpp:706:35: error: 'getppid' was not declared in this scope
linux/qsysteminfo_linux.cpp: In member function 'bool QtMobility::QSystemScreenSaverPrivate::isScreenSaverActive()':
linux/qsysteminfo_linux.cpp:815:35: error: 'getppid' was not declared in this scope

The file src/systeminfo/linux/qsysteminfo_linux.cpp (or one of its included headers) needs to #include unistd.h

It seems unistd.h was previously included by some of the C++ headers, but now isn't, so must be included when required.

Also requiring unistd.h:
plugins/multimedia/pulseaudio/qpulseaudioengine.cpp