[PECOFF] Ignore /delay and /delayload options.

These options are to enable DLL delay loading. If enabled, DLL is loaded
at run time by a helper routine when a function in the DLL is actually called
for the first time, instead of making the Windows loader to load all DLLs at
startup time. This should shorten startup delay if an executable have many
imported symbols.

The linker needs to create a "delayed import table" and link delayimp.lib in
which helper functions are defined to support the feature.

For now, we just ignore the options, so that the linker does not complain when
it sees these options. We want to support them in the future.