Remove the big/little-endian message from qtdiag's header

It's now included in QLibraryInfo::build(). That is:

Qt 5.4.0 (x86_64-little_endian-lp64 shared (dynamic) debug build; by GCC 4.8.1 20130909 [gcc-4_8-branch revision 202388]) on "xcb"

Change-Id: Ic68221f628be62ab64859ebb80059f753aa54cf1
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Print the OS version using QSysInfo

Change-Id: I1fd7df2ba131529d85ce5ffa4e99bcea63f0b8fe
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>