remove hand-written manifest

it seems that with msvc 2008 (now the first supported version)
the necessary entry is added to the auto-generated manifest, so get rid
of the hand-written one.

Change-Id: Ibc49ee246f28e432f2ff0b2fedc32dd3aa620c7f
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>