fix Windows debug build

Botan is now always built in release mode.
Don't try to link Botand.lib.

Change-Id: Ie38314abff49261589990a4fd5e7214e49b303e4
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Christian Kandeler <christian.kandeler@nokia.com>

src/libs/3rdparty/botan/botan.pri

 INCLUDEPATH *= $$PWD/..
-LIBS *= -l$$qtLibraryName(Botan)
+LIBS += -lBotan         # Don't use qtLibraryName. Botan is always built in release mode.