Fixed win32 install dir

Install dlls in <prefix>/bin instead of <prefix>/lib

By the way I've got:
    find_program(CORRADE_RC_EXECUTABLE corrade-rc)
    if(NOT CORRADE_RC_EXECUTABLE)
        message(FATAL_ERROR "Native `corrade-rc` executable, which is needed when crosscompiling, was not 

What the hell ? do you mean CMAKE_RC_COMPILER ?

x.