Please add documentation for KDE4_ENABLE_UAC_MANIFEST

[Alexander Neundorf]

Hi,

in the 4.3 cycle a new option KDE4_ENABLE_UAC_MANIFEST has been added to 
FindKDE4Internal.cmake.
The one thing that is still missing is documentation for it.
Please add documentation for this option at the top of FindKDE4Internal.cmake, 
both in trunk and 4.3 branch.

Thanks
Alex